KR100336534B1 - Method for preparing polypropylene terephthalate/polyethylene terephthalate copolyester - Google Patents

Abstract

The present invention provides a process for producing polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester, more specifically, one process selected from the group consisting of process (a) to process (e) It provides a method for producing a polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester comprising a. Process (a) is carried out by esterification of bis-2-hydroxyethyl terephthalate (BHET), purified terephthalic acid (PTA) and 1,3-propanediol (1,3-PDO) to BHET and bis-2-hydride. Producing oxypropyl terephthalate (BHPT) followed by polycondensation of BHET and BHPT. Process (b) involves esterifying PTA with 1,3-PDO to produce BHPT, and adding BHET to polycondensate BHET and BHPT. Process (c) involves polycondensation of BHET and BHPT. Process (d) involves esterifying PTA, ethylene glycol (EG) and 1,3-PDO to produce BHET and BHPT and then condensation polymerization of BHET and BHPT. Process (e) involves esterifying BHPT, PTA and EG to produce BHPT and BHET, followed by polycondensation of BHET and BHPT. Preferred PPT / PET copolyesters obtained by the present invention have the following properties: intrinsic viscosity (IV)> 0.6 dl / g, acid value (-COOH amont) <40 meq / kg, melting point (T _m ) = 190 −250 ° C., L ^* 60, b ^* <12. Thus, the PPT / PET copolyesters of the invention are suitable for use as fibers or industrial plastics.

Description

Method for preparing polypropylene terephthalate / polyethylene terephthalate copolyester {Method for preparing polypropylene terephthalate / polyethylene terephthalate copolyester}

The present invention relates to a process for the preparation of copolyesters of polypropylene terephthalate / polyethylene terephthalate (hereinafter PPT / PET copolyester), in particular the present invention being selected from process (a) -process (e) It relates to a method for producing PPT / PET copolyester by the step. Process (a) herein refers to the copolymerization reaction of BHET, PTA and 1,3-PDO via an esterification reaction; Process (b) means to esterify PTA and 1,3-PDO, and then copolymerize by adding BHET; Process (c) is to directly copolymerize BHET and BHPT; Process (d) means that PTA, ethylene glycol (EG) and 1,3-PDO are first esterified and then copolymerized; Process (e) refers to first esterification of BHPT, PTA and EG and then copolymerization.

Generally, polyethylene terephthalate (PET) is a high strength, high elastic material, but difficult to dye deep. Polypropylene terephthalate (PPT), on the other hand, is easily dyed and has a high elastic resilience, but has the disadvantage of having low strength and low melting point.

Therefore, many efforts have been made to improve the dyeability of PET fibers. As can be seen in US Patent 4,049,633 (1977), US Patent 4,029,637 (1977), US Patent 4,029,638 (1977) and US Patent 4,668,764 (1987), dyeing auxilliary agents are added during the polymerization process to obtain the polyester. . Commonly used color aids include N, N, N ', N'-tetramethyl-1,8-diaminonaphthalene, N- (β-hydroxyethyl) -N- (3-carbomethoxybenzsul Polyvinyl) taurine, alkali metal salts of N-benzyl-N-propyl sulfonate benzene sulfonamide, 1,4-cyclohexanedimethanol, 2,2-bis-propane and the like. As mentioned above, the dyeability of the copolyester can be improved by the addition of a dyeing aid, but the processability is reduced, adversely affecting the overall process. For example, commercial PET fibers that can be dyed with basic dyes not only have lower strength than traditional polyester fibers, but also have a shorter pack life during melt spinning than traditional polyester. Moreover, PET that can be dyed with basic dyes has the disadvantage that it cannot be produced continuously.

Therefore, the researchers attempted to copolymerize PPT and PET together to make a new polyester with improved physical properties. Ponnusamy and Balakrishnan have developed a PET / PPT copolyester, produced by reacting dimethyl terephthalate (DMT), ethylene glycol and 1,3-propanediol by melt-condensation polymerization (J. Macromol. Sci. -Chem., A22 (3), pp. 373-378 (1985)) However, even though DMT is a very expensive compound, it is difficult to recover by-product methanol. In addition, PET / PPT copolyesters obtained by melt-condensation polymerization have so low molecular weight that their maximum intrinsic viscosity is only 0.4 dL / g, which is not practical.

On the other hand, Yang Ho Park et al. Developed another PET / PP copolyester that polycondensates PET oligomers with 1,3-propanediol (abbreviated as 1,3-PDO or PG). (Journal of the Korean Fiber Society, vol. 36, No. 7, 1999) PET oligomers (BHET) only react with the terminal residuals of PG compounds. Therefore, in theory, in the copolyester product, the bis-2-hydroxypropyl terephthalate (BHPT) obtained is very limited. Moreover, the reaction temperature is 240-280 ° C., which exceeds the boiling point of PG. In addition, the alcohol of the PET oligomer is reacted with 1,3-propanediol by an exchange reaction and then produced by PPT / PET copolyester by a condensation polymerization reaction. Ethylene glycol, a byproduct produced during the exchange reaction, must be removed, thus increasing production costs.

The present invention is to solve the above problems, an object of the present invention to provide a method for producing polypropylene terephthalate / polyethylene terephthalate (PPT / PET).

The present invention is the starting material of purified terephthalic acid (TPA), ethylene glycol (EG) and 1,3-propanediol (PDO), which are inexpensive and commercially available; In addition, the reaction can be carried out in a conventional PET reactor or a conventional PPT reactor. The resulting PPT / PET copolyester has the following properties: intrinsic viscosity (IV)> 0.6 dl / g, acid value (-COOH amount) <40 meq / kg, mp = 190-250 ° C., L ^* 60, b ^* 12.

According to a preferred embodiment of the present invention, the PPT / PET copolyester has a BHPT chain of 5 to 7.5 wt%, which is suitable for use as a fiber or industrial plastic.

In order to achieve the object of the present invention, the process for preparing polypropylene terephthalate / polyethylene terephthalate (PPT / PET) comprises using a process chosen between process (a) and process (e).

From here:

Process (a) is carried out by esterification of bis-2-hydroxyethyl terephthalate (BHET), purified terephthalic acid (PTA) and 1,3-propanediol (1,3-PDO) to the BHET and bis-2-hydride. Producing oxypropyl terephthalate (BHPT) followed by copolymerization of BHET and BHPT;

Process (b) involves esterifying PTA with 1,3-PDO to make BHPT, and adding BHET to copolymerize BHET and BHPT.

Process (c) involves copolymerizing BHET and BHPT.

Process (d) involves esterifying PTA, ethylene glycol (EG) and 1,3-PDO to form BHET and BHPT, and then copolymerizing BHET and BHPT.

Process (e) involves esterifying BHPT, PTA and EG to produce BHPT and BHET, and then copolymerizing BHET and BHPT.

Comparing the PET fiber manufacturing method with improved dyeability compared to the existing process, the present invention does not include a dyeing aid monomer, the copolyester of the present invention includes a PET molecular chain and PPT molecular chain connecting each other. In addition, traditional devices for producing polyester (such as PET or PPT) can be used in the present invention. The PPT / PET copolyesters of the present invention have good dyeing properties as PPT and good physical properties as PET and PPT.

Ponnusamy and Balakrishnan used DMT as a starting material for producing PET or PPT, but DMT itself is not commercially accessible and expensive. In addition, methanol, a byproduct, must be removed by a separate recovery process, which inevitably increases production costs. On the other hand, the present invention uses purified terephthalic acid (PTA) as a starting material. The process according to the invention is more convenient since the starting materials of the invention are more accessible, which reduces the overall production cost.

The purified terephthalic acid (PTA) monomers used in processes (a), (b), (d) and (e) are of fiber grade and preferably have the following properties: acid value = 675 ± 2, 4 CBA (4 -Carboxybenzaldehyde) ≤ 25 ppm, ash ≤ 15 ppm, metal ≤ 2 ppm, molecular weight = 166.13 g / mol, particle size ≤ 75μ.

The 1,3-propanediol used in the processes (a), (b) and (d) preferably has the following properties: purity> 99%, moisture content <2 wt%, molecular weight = 76.10 g / mol, mp is about −32 ° C., boiling point about 214 ° C. (at atmospheric pressure).

The ethylene glycol used in the processes (d) and (e) preferably has the following properties: purity of at least 98.5%, more preferably at least 99%, moisture content <2 wt%, more preferably <0.005 wt %, Molecular weight = 62.07 g / mol, mp About −13 ° C., boiling point about 197.2 ° C., flash point = 111.1 ° C. (in closed system), specific gravity = 1.1336 (20/20 ° C.).

In processes (a) and (b), the molar ratio of 1,3-propanediol to purified terephthalic acid is preferably in the range from 1.3 to 2.4.

The bis-2-hydroxyethyl terephthalate (BHET) used in the processes (a), (b) and (c) preferably has the following properties: acid value = 28 ± 8 KOH mg / g, saponification value = 558 ± 20 KOH mg / g, change ratio = 95 ± 1.5%, free ethylene glycol ≦ 4%. In addition, the BHET used in the present invention is preferably obtained by reacting ethylene glycol and purified terephthalic acid at a molar ratio of 1.0 to 2.4, more preferably at a molar ratio of 1.2 to 1.5.

The bis-2-hydroxypropyl terephthalate (BHPT) used in the processes (c) and (e) preferably has the following properties: acid value = 3.76 ± 0.5 KOH mg / g, saponification value = 506 ± 20 KOH mg / g, conversion ratio = 98 ± 1.5%, free propylene glycol <0.046%. In addition, the BHPT used in the present invention is preferably obtained by reacting 1,3-propanediol and purified terephthalic acid at a molar ratio of 1.0 to 2.4, more preferably at a molar ratio of 1.2 to 1.5.

In the processes (a), (b), (d) and (e), the esterification reaction is preferably performed in the presence of an esterification catalyst. As a suitable esterification catalyst, tetraethylene titanate, tetrabutylene titanate, or a mixture thereof can be used, and it is preferable to use about 100-300 ppm with respect to the total weight of the purified terephthalic acid.

In processes (a) to (e), the copolymerization is preferably carried out in the presence of a polymerization catalyst such as antimony acetate or antimony trioxide. The polymerization catalyst is 100 to 300 with respect to the total weight of the purified terephthalic acid. It is preferred that amounts of ppm are present. In process (c), the polymerization catalyst is preferably present in an amount of about 100 to 300 ppm relative to the total weight of the purified terephthalic acid used in the production of BHET and BHPT.

During the copolymerization reaction of the present invention, a cocatalyst may be further added to make copolymerization easier. Suitable cocatalysts for use in the present invention include cobalt acetate, manganese acetate, magnesium acetate, calcium acetate, sodium acetate and the like. The amount of use is preferably 30 to 150 ppm based on the total weight of the purified terephthalic acid. In process (c), the cocatalyst is preferably present in an amount of 30 to 150 ppm relative to the total weight of the purified terephthalic acid used in the preparation of BHET and BHPT. In the case of using cobalt acetate, the amount is preferably 5 to 50 ppm by weight of the purified terephthalic acid.

Thermal stabilizers such as trivalent phosphate esters or phosphate salts may be added during the copolymerization reaction of the present invention to improve the thermal stability of the produced BHET, BHPT or PPT / PET copolyesters. Representative examples of heat stabilizers include sodium dihydrogen phosphate and triphenyl phosphate. An amount of about 10 to 20 ppm by weight of the purified terephthalic acid is preferred.

In the processes (a), (b), (d) and (e), the esterification reaction is preferably performed at a temperature of 200 to 255 ° C, more preferably at a temperature of 220 to 250 ° C, and the pressure is 1 to 3.5 atm. The following prepolymerization reaction is preferably carried out in a vacuum of 30 torr or less at a temperature of 230 to 252 ° C, more preferably in a vacuum of 760 torr to 4 torr at a temperature of 245 to 250 ° C. The copolymerization reaction is preferably carried out in a vacuum of 2.5 torr or less at a temperature of 240 to 275 ° C, and more preferably in a vacuum of 1.5 torr or less at a temperature of 240 to 270 ° C.

Basically, PPT / PET copolyesters with different weight ratios of BHPT and BHET can be obtained by any of the processes (a) to (e) according to the invention, wherein the range of IV values is 0.63-0.89 dl / g.

The molten polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester obtained by the present invention is spun onto filaments and cut into granules. PPT / PET copolyester in cut granule form was completely dried, and the following physical properties were measured.

(1) Intrinsic viscosity (IV): measured according to the method of ASTM D4603-91.

(2) Acid value (-COOH amount): measured according to the method of PV-07013.4 Zimmer Eng. Company, Germany.

(3) Melting point (m.p.): Measured by DSC according to JIS K7121-1987 method.

(4) Color: To determine the values of L and b ^* of the PPT / PET copolyester granules, they were measured according to the methods of ASTM E398-90 and E805-93.

(5) Saponification value: measured according to the method of PV-09009.2 Zimmer Eng. Company, Germany.

(6) Conversion rate: PV-07026.4 was measured according to the method of Zimmer Eng. Company, Germany.

(7) Free ethylene glycol: PV-07027.3 It measured according to the method of Zimmer Eng. Company, Germany.

(8) Glass 1,3-propanediol: PV-07027.3 It measured according to the method of Zimmer Eng. Company, Germany.

In the following examples, it can be seen that the PPT / PET copolyester obtained by the present invention has the following characteristics: intrinsic viscosity (IV)> 0.6 dl / g, acid value (-COOH amount) <40 meq / kg , Melting point = 190-250 ° C., L ^* 60, b ^* <12.

The following examples are intended to illustrate the methods and advantages of the present invention in more detail, and are not intended to limit the scope thereof, and that various modifications and changes are possible, which will be apparent to those of ordinary skill in the art.

Example 1

In this embodiment, the weight ratio of BHET / BHPT is set to 20/80. 181.6 g of purified terephthalic acid (PTA) was added to the reaction vessel, and 166.4 g of 1,3-propanediol (1,3-PDO) was added thereto. At this time, the molar ratio of 1,3-PDO and PTA is 2.0. 77.2 g of bis-2-hydroxyethyl terephthalate (BHET) are added first, followed by 100 ppm of tetraethylene titanate (to the total weight of PTA) as catalyst of the esterification reaction. Stir slowly with a stirrer to ensure that the contents in the vessel are evenly mixed and remove any residual air using a 200 mL / min nitrogen stream. Increase the pressure in the reaction vessel to 2 kg / cm ² using a nitrogen stream of 100 mL / min. The reaction vessel is heated to 238 ° C with stirring at a speed of 80 rpm. The esterification reaction is terminated after 1.42 hours or when substantially up to 96% of the theoretical water is produced.

The pressure is reduced and the polymerization catalyst (250 ppm antimony acetate for PTA total weight) and polymerization cocatalyst (40 ppm cobalt acetate for PTA weight) are added under constant stirring at a speed of 80 rpm. The temperature of the reaction vessel is continuously heated to 254 ° C. so that the polymerization takes place, and the pressure is gradually reduced to vacuum. In the prepolymerization stage, the temperature is 230-252 ° C., and the vacuum is 30 torr or less. After 2.1 hours the applied voltage of the stirrer reaches its maximum. When the maximum voltage is reached and equilibrated for 0.5 hours, the polymerization is terminated, and the vacuum is about 0.8 torr.

The resulting polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester is spun onto the filaments and then cut into granules.

After drying the granulated PPT / PET copolyester, various physical properties were measured. The measurement result was as follows: IV = 0.8239, acid value = 17.89 meq / kg, T _m = 221.23 ° C, T _g = 49.39 ° C, L ^* = 82.62, b ^* = 9.75. These reaction conditions and results are summarized in Tables 1,2,3.

Example 2

In this embodiment, the weight ratio of BHET / BHPT is 40/60. 136.3 g of purified terephthalic acid (PTA) was added to the reaction vessel, and 99.87 g of 1,3-propanediol (1,3-PDO) was added thereto. At this time, the molar ratio of 1,3-PDO and PTA is 1.6. 154.4 g of bis-2-hydroxyethyl terephthalate (BHET) is added first, followed by 100 ppm tetraethylene titanate (by weight of PTA) as catalyst of the esterification reaction. Stir slowly with a stirrer to ensure that the contents in the vessel are evenly mixed and remove any residual air using a 200 mL / min nitrogen stream. Increase the pressure in the reaction vessel to 2 kg / cm ² using a nitrogen stream of 100 mL / min. The reaction vessel is heated to 242 ° C while stirring at a speed of 80 rpm. The esterification reaction is terminated after 3.67 hours or when substantially up to 96% of the theoretical water is produced.

The pressure is reduced and the polymerization catalyst (250 ppm of antimony acetate for the total weight of PTA) and the polymerization cocatalyst (40 ppm of cobalt acetate for weight of the PTA) are added under constant stirring at 80 rpm. The heating of the reaction vessel is continued to bring the temperature of the reaction vessel to 253 ° C, and the pressure is gradually reduced to a vacuum state so that the polymerization reaction occurs. In the prepolymerization stage, the temperature is 230-252 ° C., and the vacuum is 30 torr or less. After 2.08 hours the applied voltage of the stirrer reaches its maximum. When the maximum voltage is reached and kept in equilibrium for 0.5 hours, the polymerization is terminated, at which time the vacuum is about 0.95 torr.

The resulting polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester is spun onto the filaments and then cut into granules.

After drying the granulated PPT / PET copolyester, various physical properties were measured. The measurement results are as follows: IV = 0.7557, acid value = 12.42 meq / kg, T _m = 190.68 ° C, T _g = -54.75 ° C, L ^* = 78.77, b ^* = 5.45. These reaction conditions and results are summarized in Tables 1,2,3.

Example 3

In this embodiment, the weight ratio of BHET / BHPT is 60/40. 96.3 g of purified terephthalic acid (PTA) was added to the reaction vessel and 88.2 g of 1,3-propanediol (1,3-PDO) was added thereto. At this time, the molar ratio of 1,3-PDO and PTA is 2.0. 231.6 g of bis-2-hydroxyethyl terephthalate (BHET) are added first, followed by 100 ppm tetraethylene titanate (by weight of PTA) as catalyst of the esterification reaction. Stir slowly with a stirrer to ensure that the contents in the vessel are evenly mixed and remove any residual air using a 200 mL / min nitrogen stream. Increase the pressure in the reaction vessel to 2 kg / cm ² using a nitrogen stream of 100 mL / min. The reaction vessel is heated to 242 ° C while stirring at a speed of 80 rpm. The esterification reaction is terminated after 2.37 hours or when substantially up to 96% of the theoretical water is produced.

The pressure is reduced and the polymerization catalyst (250 ppm antimony acetate for PTA total weight) and polymerization cocatalyst (40 ppm cobalt acetate for PTA weight) are added under constant stirring at a speed of 80 rpm. The heating of the reaction vessel is continued until the temperature of the reaction vessel is 256 ° C, and the pressure is gradually reduced to a vacuum state so that the polymerization reaction occurs. In the prepolymerization stage, the temperature is 230-252 ° C., and the vacuum is 30 torr or less. After 2 hours the applied voltage of the stirrer reaches its maximum. When the maximum voltage is reached and equilibrated for 0.5 hours, the polymerization is terminated, and the vacuum is about 1.1 torr. The resulting polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester is spun onto the filaments and then cut into granules.

After drying the granulated PPT / PET copolyester, various physical properties were measured. The measurement result was as follows: IV = 0.7117, acid value = 19.76 meq / kg, T _g = 55.93 ° C, L ^* = 83.92, b ^* = 6.16. These reaction conditions and results are summarized in Tables 1,2,3.

Example 4

In this embodiment, the weight ratio of BHET / BHPT is set to 80/20. 45.4 g of purified terephthalic acid (PTA) was added to the reaction vessel and 49.94 g of 1,3-propanediol (1,3-PDO) was added thereto. At this time, the molar ratio of 1,3-PDO and PTA is 2.4. 308.8 g of bis-2-hydroxyethyl terephthalate (BHET) is added first, and 100 ppm of tetraethylene titanate (by weight of PTA) is added as a catalyst for the esterification reaction. Stir slowly with a stirrer to ensure that the contents in the vessel are evenly mixed and remove any residual air using a 200 mL / min nitrogen stream. Increase the pressure in the reaction vessel to 2 kg / cm ² using a nitrogen stream of 100 mL / min. The reaction vessel is heated to 238 ° C with stirring at a speed of 80 rpm. The esterification reaction is terminated after 1.75 hours or when substantially up to 96% of theoretical water is produced.

Reduce the pressure and add the polymerization catalyst (195.7 ppm of antimoniacetate for PTA total weight) and polymerization cocatalyst (31.3 ppm of cobalt acetate for PTA weight) under constant stirring at 80 rpm. The heating of the reaction vessel is continued until the temperature of the reaction vessel is 254 ° C., and the pressure is gradually reduced to a vacuum state. In the prepolymerization stage, the temperature is 230-252 ° C., and the vacuum is 30 torr or less. After 2 hours the applied voltage of the stirrer reaches its maximum. When the maximum voltage is reached and kept in equilibrium for 0.5 hours, the polymerization is terminated, and the vacuum is about 1 torr.

The resulting polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester is spun onto the filaments and then cut into granules.

After drying the granulated PPT / PET copolyester, various physical properties were measured. The measurement result was as follows: IV = 0.6358, acid value = 10.10 meq / kg, T _g = 68.89 ° C, L ^* = 85.73, b ^* = 5.39. These reaction conditions and results are summarized in Tables 1,2,3.

Example 5

In this embodiment, the weight ratio of BHET / BHPT is set to 90/10. 22.7 g of purified terephthalic acid (PTA) was added to the reaction vessel and 24.97 g of 1,3-propanediol (1,3-PDO) was added thereto. At this time, the molar ratio of 1,3-PDO and PTA is 2.4. 347.4 g of bis-2-hydroxyethyl terephthalate (BHET) is added first, followed by 100 ppm tetraethylene titanate (by weight of PTA) as catalyst of the esterification reaction. Stir slowly with a stirrer to ensure that the contents in the vessel are evenly mixed and remove any residual air using a 200 mL / min nitrogen stream. Increase the pressure in the reaction vessel to 2 kg / cm ² using a nitrogen stream of 100 mL / min. The reaction vessel is heated to 243 ° C. while stirring at 80 rpm. The esterification reaction is terminated after 2.5 hours or when substantially up to 96% of the theoretical water is produced.

The pressure is reduced and the polymerization catalyst (250 ppm antimony acetate for PTA total weight) and polymerization cocatalyst (40 ppm cobalt acetate for PTA weight) are added under constant stirring at a speed of 80 rpm. In order to cause the polymerization reaction, the temperature of the reaction vessel is continuously heated to 256 ° C., and the pressure is gradually reduced to the vacuum state. In the prepolymerization stage, the temperature is 230-252 ° C., and the vacuum is 30 torr or less. After 2.2 hours, the applied voltage of the stirrer reaches its maximum. When the maximum voltage is reached and kept in equilibrium for 0.5 hours, the polymerization is terminated, at which time the vacuum is about 0.78 torr. The resulting polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester is spun onto the filaments and then cut into granules.

After drying the granulated PPT / PET copolyester, various physical properties were measured. The measurement result was as follows: IV = 0.6279, acid value = 8.45 meq / kg, T _m = 221.87 ° C, T _g = 69.65 ° C, L ^* = 82.16, b ^* = 3.7. These reaction conditions and results are summarized in Tables 1,2,3.

Example 6

In this embodiment, the weight ratio of BHET / BHPT is set to 95/5. 11.4 g of purified terephthalic acid (PTA) was added to the reaction vessel, and 12.48 g of 1,3-propanediol (1,3-PDO) was added thereto. At this time, the molar ratio of 1,3-PDO and PTA is 2.4. 366.7 g of bis-2-hydroxyethyl terephthalate (BHET) are added first, followed by 100 ppm of tetraethylene titanate (to the total weight of PTA) as catalyst of the esterification reaction. Stir slowly with a stirrer to ensure that the contents in the vessel are evenly mixed and remove any residual air using a 200 mL / min nitrogen stream. Increase the pressure in the reaction vessel to 2 kg / cm ² using a nitrogen stream of 100 mL / min. The reaction vessel is heated to 243 ° C. while stirring at 80 rpm. The esterification reaction is terminated after 0.83 hours or when substantially up to 96% of the theoretical water is produced.

The pressure is reduced and the polymerization catalyst (250 ppm antimony acetate for PTA total weight) and polymerization cocatalyst (40 ppm cobalt acetate for PTA weight) are added under constant stirring at a speed of 80 rpm. In order to cause the polymerization reaction, the temperature of the reaction vessel is continuously heated to 259 ° C., and the pressure is gradually reduced to the vacuum state. In the prepolymerization stage, the temperature is 230-252 ° C., and the vacuum is 30 torr or less. After 2 hours the applied voltage of the stirrer reaches its maximum. When the maximum voltage is reached and equilibrated for 0.5 hours, the polymerization is terminated, at which time the vacuum is about 1 torr.

The resulting polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester is spun onto the filaments and then cut into granules.

After drying the granulated PPT / PET copolyester, various physical properties were measured. The measurement result was as follows: IV = 0.6383, acid value = 17.07 meq / kg, T _m = 239.37 ° C, T _g = 72.87 ° C, L ^* = 82.74, b ^* = 3.83. These reaction conditions and results are summarized in Tables 1,2,3.

Example 7

In this embodiment, the weight ratio of BHET / BHPT is 92.5 / 7.5. 22.7 g of purified terephthalic acid (PTA) was added to the reaction vessel and 24.97 g of 1,3-propanediol (1,3-PDO) was added thereto. At this time, the molar ratio of 1,3-PDO and PTA is 2.4. 154.4 g of bis-2-hydroxyethyl terephthalate (BHET) is added first, followed by 100 ppm tetraethylene titanate (by weight of PTA) as catalyst of the esterification reaction. Stir slowly with a stirrer to ensure that the contents in the vessel are evenly mixed and remove any residual air using a 200 mL / min nitrogen stream. Increase the pressure in the reaction vessel to 2 kg / cm ² using a nitrogen stream of 100 mL / min. The reaction vessel is heated to 243 ° C. while stirring at 80 rpm. The esterification reaction is terminated after 1.33 hours or when substantially up to 96% of the theoretical water is produced.

The pressure is reduced and the polymerization catalyst (250 ppm antimony acetate for PTA total weight) and polymerization cocatalyst (40 ppm cobalt acetate for PTA weight) are added under constant stirring at a speed of 80 rpm. The heating is continued to bring the temperature of the reaction vessel to 259 ° C. so that the polymerization takes place, and the pressure is gradually reduced to vacuum. In the prepolymerization stage, the temperature is 230-252 ° C., and the vacuum is 30 torr or less. After 2.08 hours the applied voltage of the stirrer reaches its maximum. When the maximum voltage is reached and kept in equilibrium for 0.5 hours, the polymerization is terminated, at which time the vacuum is about 0.95 torr. The resulting polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester is spun onto the filaments and then cut into granules.

After drying the granulated PPT / PET copolyester, various physical properties were measured. The measurement results are as follows: IV = 0.6561, acid value = 11.05 meq / kg, T _m = 230 ° C, T _g = 61 ° C, L ^* = 84.45, b ^* = 3.01. These reaction conditions and results are summarized in Tables 1,2,3.

Example 8

In this embodiment, the weight ratio of BHET / BHPT is set to 95/5. 11.4 g of purified terephthalic acid (PTA) was added to the reaction vessel, and 12.5 g of 1,3-propanediol (1,3-PDO) was added thereto. At this time, the molar ratio of 1,3-PDO and PTA is 2.4. 100 ppm tetraethylene titanate (relative to PTA weight) is added as a catalyst for the esterification reaction. Stir slowly with a stirrer to ensure that the contents in the vessel are evenly mixed and remove any residual air using a 200 mL / min nitrogen stream. Increase the pressure in the reaction vessel to 2 kg / cm ² using a nitrogen stream of 100 mL / min. The reaction vessel is heated to 241 ° C. while stirring at 80 rpm. The esterification reaction is terminated after 2.83 hours or when substantially up to 96% of the theoretical water is produced.

Reduce the pressure and add 366.7 g of BHET and the polymerization catalyst (250 ppm antimony acetate for the total weight of PTA) and the polymerization cocatalyst (40 ppm cobalt acetate for the weight of the PTA) under constant stirring at 80 rpm. . The temperature of the reaction vessel is continued to 258 ° C. and the pressure is gradually reduced to a vacuum state so that the polymerization reaction occurs. In the prepolymerization stage, the temperature is 230-252 ° C., and the vacuum is 30 torr or less. After 2.18 hours the applied voltage of the stirrer reaches its maximum. When the maximum voltage is reached and kept in equilibrium for 0.5 hours, the polymerization is terminated, and the vacuum is about 1.2 torr.

The resulting polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester is spun onto the filaments and then cut into granules.

After drying the granulated PPT / PET copolyester, various physical properties were measured. The measurement result was as follows: IV = 0.6773, acid value = 28.16 meq / kg, T _m = 224.86 ° C, T _g = 74.32 ° C, L ^* = 77.96, b ^* = 7.77. These reaction conditions and results are summarized in Tables 1,2,3.

Example 9

In this embodiment, the weight ratio of BHET / BHPT is set to 95/5. 366.7 g of bis-2-hydroxyethyl terephthalate (BHET) was added to the reaction vessel, where 19.3 g of bis-2-hydroxypropyl terephthalate (BHPT) and a polymerization catalyst (250 ppm of antimony acetate by weight of PTA) were added. And a polymerization cocatalyst (40 ppm cobalt acetate by weight of PTA) (BHET can be obtained by the reaction of PTA with ethylene glycol, and BHPT can be obtained by the reaction of PTA with 1,3-propanediol). 50 mL / min nitrogen stream is used to remove residual air. The reaction vessel is continuously heated to 259 ° C. so that the polymerization takes place while stirring at a speed of 80 rpm and the pressure is gradually reduced to vacuum. In the prepolymerization stage, the temperature is 230-252 ° C., and the vacuum is 30 torr or less. After 1.45 hours the applied voltage of the stirrer reaches its maximum. When the maximum voltage is reached and kept in equilibrium for 0.5 hours, the polymerization is terminated, at which time the vacuum is about 1.05 torr.

The resulting polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester is spun onto the filaments and then cut into granules.

After drying the granulated PPT / PET copolyester, various physical properties were measured. The measurement result was as follows: IV = 0.7279, acid value = 23.38 meq / kg, T _m = 245.17 ° C, T _g = 66.53 ° C, L ^* = 77.66, b ^* = 8.5. These reaction conditions and results are summarized in Tables 1,2,3.

Example 10

In this embodiment, the weight ratio of BHET / BHPT is set to 95/5. 251 g of purified terephthalic acid (PTA) was added to the reaction vessel, and 6.24 g of 1,3-propanediol (1,3-PDO) was added thereto. At this time, the molar ratio of 1,3-PDO and PTA is 1.2. Then, 107.4 g of ethylene glycol (EG) is added, wherein the molar ratio of EG and PTA is 1.2. Next, a catalyst for esterification reaction (100 ppm tetraethylene titanate by weight of PTA) and a polymerization catalyst (250 ppm antimony trioxide by weight of PTA) are added. Stir slowly with a stirrer to ensure that the contents in the vessel are evenly mixed and remove any residual air using a 200 mL / min nitrogen stream. Increase the pressure in the reaction vessel to 3.5 kg / cm ² using 100 mL / min nitrogen stream. The reaction vessel is heated to 240 ° C. while stirring at a speed of 80 rpm. The esterification reaction is terminated after 7 hours or when substantially up to 96% of the theoretical water is produced.

The pressure is reduced and the polymerization cocatalyst (40 ppm of cobalt acetate by weight of PTA) is added under constant stirring at a speed of 80 rpm. The heating is continued to bring the temperature of the reaction vessel to 259 ° C. so that the polymerization takes place, and the pressure is gradually reduced to vacuum. In the prepolymerization stage, the temperature is 230-252 ° C., and the vacuum is 30 torr or less. After 1.5 hours the applied voltage of the stirrer reaches its maximum. When the maximum voltage is reached and kept in equilibrium for 0.5 hours, the polymerization is terminated, and the vacuum is about 1.5 torr.

The resulting polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester is spun onto the filaments and then cut into granules.

After drying the granulated PPT / PET copolyester, various physical properties were measured. The measurement result was as follows: IV = 0.6434, acid value = 26.03 meq / kg, T _m = 241.59 ° C, T _g = 67.53 ° C, L ^* = 74.03, b ^* = 5.44. These reaction conditions and results are summarized in Tables 1,2,3.

Example 11

In this embodiment, the weight ratio of BHET / BHPT is 95/5, and the molar ratio of EG and PTA is 1.3. In a 200 L esterification vessel, 4.5 kg of BHPT, 55 kg of PTA, EG27 kg and 300 ppm of antimony trioxide (by weight of PTA) were added as polymerization catalyst. Tetrabutylene titanate is used as catalyst for the esterification reaction for the preparation of BHPT. The contents of the vessel are washed with a nitrogen stream of 4 L / min and stirred uniformly at a stirring speed of 130 rpm under a reaction pressure of 2 kg / cm ² . Raise the inner temperature of the vessel to 255 ℃. By-product water and EG are separated by a separation tower during the esterification reaction so that water is collected at the top of the separation tower. After 3.3 hours of esterification, the esterified product is transferred to the polymerization vessel.

The esterified product is subjected to prepolymerization and polymerization in a polymerization vessel. After 50 minutes, the pressure is reduced to a vacuum of 1 torr. In the prepolymerization stage, the temperature is 230-252 ° C., and the vacuum is 30 torr or less. In the polymerization step, the temperature is 255 to 270 ° C and the vacuum is 1 torr. Stirring speed was 60 rpm during treatment and slowed down to 30 rpm. The overall polymerization time was 3.5 hours.

The resulting polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester is spun onto the filaments and then cut into granules.

After drying the granulated PPT / PET copolyester, various physical properties were measured. The measurement results are as follows: IV = 0.6164, acid value = 15.96 meq / kg, T _m = 239.80 ° C, T _g = 70.54 ° C, L ^* = 62.88, b ^* = 8.03. These reaction conditions and results are summarized in Tables 1,2,3.

Example 12

In this embodiment, the weight ratio of BHET / BHPT is 80/20, and the molar ratio of EG and PTA is 1.3. In a 200 L esterification vessel, 19.1 kg BHPT, 50 kg PTA, 24 .3 kg EG and 300 ppm antimony trioxide (by weight of PTA) are added as polymerization catalyst. For the preparation of BHPT, tetrabutylene titanate was used as catalyst for esterification reaction. The contents of the vessel are washed with a nitrogen stream of 4 L / min and stirred uniformly at a stirring speed of 130 rpm under a reaction pressure of 2 kg / cm ² . Raise the inner temperature of the vessel to 245 ℃. By-product water and EG were separated by a separation tower during the esterification reaction, and water was collected at the top of the separation tower. After 3.5 hours of esterification reaction, the esterified product is transferred to the polymerization vessel.

The esterified product is subjected to prepolymerization and polymerization in a polymerization vessel. After 50 minutes, the pressure is reduced to a vacuum of 1 torr. In the prepolymerization stage, the temperature is 230-252 ° C., and the vacuum is 30 torr or less. In the polymerization step, the temperature is 245 to 255 ° C and the vacuum is 1 torr. During the prepolymerization and polymerization process, the stirring speed was initially 60 rpm, but was finally slowed down to 30 rpm. The total polymerization time was 4 hours.

The resulting polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester is spun onto the filaments and then cut into granules.

After drying the granulated PPT / PET copolyester, various physical properties were measured. The measurement result was as follows: IV = 0.6325, acid value = 11.26 meq / kg, T _m = 201.36 ° C, T _g = 65.59 ° C, L ^* = 62.88, b ^* = 10.31. These reaction conditions and results are summarized in Tables 1,2,3.

Example 13

In this embodiment, the weight ratio of BHET / BHPT is 84/16, and the molar ratio of EG and PTA is 1.3. In a 200 L esterification vessel, 12 kg of BHPT, 40 kg of PTA, 19.4 kg of EG and 300 ppm of antimony trioxide (by weight of PTA) were added as polymerization catalyst. Tetrabutylene titanate is used as catalyst for the esterification reaction for the preparation of BHPT. The contents of the vessel are washed with a nitrogen stream of 4 L / min and stirred uniformly at a stirring speed of 130 rpm under a reaction pressure of 2 kg / cm ² . The internal temperature of the vessel is raised to 250 ° C. By-product water and EG are separated by a separation tower during the esterification reaction so that water is collected at the top of the separation tower. After 4 hours of esterification reaction, the esterified product is transferred to the polymerization vessel.

The esterified product is subjected to prepolymerization and polymerization in a polymerization vessel. The pressure is reduced to a vacuum of 1 torr after 50 minutes. In the prepolymerization stage, the temperature is 230-252 ° C., and the vacuum is 30 torr or less. In the polymerization step, the temperature is 245 to 255 ° C and the vacuum is 1 torr. During the prepolymerization and polymerization process, the stirring speed was initially 60 rpm, but was finally slowed down to 30 rpm. The total polymerization time was 3.3 hours.

The resulting polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester is spun onto the filaments and then cut into granules.

After drying the granulated PPT / PET copolyester, various physical properties were measured. The measurement result was as follows: IV = 0.6381, acid value = 25.86 meq / kg, T _m = 206.26 ° C, T _g = 68.73 ° C, L ^* = 62.61, b ^* = 5.62. These reaction conditions and results are summarized in Tables 1,2,3.

Comparative Example 1

In this comparative example, the weight ratio of BHET / BHPT is 40/60. 136.3 g of purified terephthalic acid (PTA) was added to the reaction vessel, and 74.9 g of 1,3-propanediol (1,3-PDO) was added thereto. At this time, the molar ratio of 1,3-PDO and PTA is 1.2. 154.4 g of bis-2-hydroxyethyl terephthalate (BHET) is added first, followed by 100 ppm of tetraethylene titanate (to the total weight of PTA) as catalyst of the esterification reaction. Stir slowly with a stirrer to ensure that the contents in the container are evenly mixed and rinsed with a 200 mL / min nitrogen stream to remove residual air. Increase the pressure in the reaction vessel to 2 kg / cm ² with a nitrogen stream of 100 mL / min. The reaction vessel is heated to 244 ° C. while stirring at 80 rpm. After 7 hours the esterification reaction is complete. On the other hand, water equivalent to 89% is actually produced rather than 96% of the theoretical value.

The pressure is reduced and the polymerization catalyst (250 ppm antimony acetate for PTA total weight) and polymerization cocatalyst (40 ppm cobalt acetate for PTA weight) are added under constant stirring at a speed of 80 rpm. The heating of the reaction vessel is continued until the temperature of the reaction vessel is 250 ° C., and the pressure is gradually reduced to vacuum. In the prepolymerization stage, the temperature is 230-252 ° C., and the vacuum is 30 torr or less. After 3.3 hours the applied voltage of the stirrer reaches its maximum. When the maximum voltage was reached and kept in equilibrium for 0.5 hours, the polymerization was terminated, and the vacuum was about 0.9 torr. The copolymer product in the molten state could not be spun onto the filaments and the desired polypropylene terephthalate / polyethylene terephthalate copolyester could not be obtained.

Comparative Example 2

In this comparative example, the weight ratio of BHET / BHPT is 100/0. 386 g of bis-2-hydroxyethyl terephthalate (BHET) was added to the reaction vessel, 250 ppm of antimony acetate (for the total weight of PTA) as the polymerization catalyst, and 40 ppm of cobalt acetate (to the weight of the PTA) were used as the polymerization cocatalyst. Put it in. Rinse the contents of the vessel with a 50 mL / min nitrogen stream to remove residual air and stir at 80 rpm. The heating of the reaction vessel is continued to bring the temperature of the reaction vessel to 258 ° C., and the pressure is gradually reduced to a vacuum state. In the prepolymerization stage, the temperature is 230-252 ° C., and the vacuum is 30 torr or less. After 2.33 hours the applied voltage of the stirrer reaches its maximum. When the maximum voltage was reached and kept in equilibrium for 0.5 hours, the polymerization was terminated, at which time the vacuum was about 1 torr.

Polyethylene terephthalate (PET) produced in the molten state is spun onto filaments and then cut into granules.

After the granulated PET was completely dried, various physical properties were measured. The measurement result was as follows: IV = 0.6383, acid value = 22.61 meq / kg, T _m = 256.29 ° C, T _g = 76.03 ° C, L ^* = 78.73, b ^* = 2.15. These reaction conditions and results are summarized in Tables 1,2,3.

Table 2. Polymerization Conditions of PPT / PET Copolyester Preparation

Example Sb (OAc) ₃ (ppm) Co (OAc) ₂ (ppm) Internal temperature (℃) Minimum vacuum (torr) T _p (hr) Stirring Speed (rpm) One 250 40 251-258 0.8 2.1 80-72 2 250 40 250-255 0.95 2.08 80-71 3 250 40 254-259 1.1 2 80-70 4 250 40 257-259 0.85 2 80-68-66 5 250 40 254-258 0.78 2.2 80-65 6 250 40 258-260 One 2 80-63 7 250 40 257-261 0.95 2.08 80-63 8 250 40 257-260 1.2 2.18 80-62 9 250 40 257-260 1.05 1.45 79-60 10 @ 250 40 257-261 0.9 1.5 79-60 11 - - 255-270 0.5 3.5 60-30 12 - - 245-255 0.7 4.0 60-30 13 - - 245-255 0.9 3.3 60-30 Comparative Example 1 250 40 250 0.9 3.33 - Comparative Example 2 250 40 256-259 One 2.33 80-63

1. T _p is the total polymerization time from low vacuum to high vacuum.

2. After the completion of the esterification reaction, the contents are continuously stirred and a polymerization catalyst is added.

3. In Example 1-7, BHET purchased from Hualon Corporation is used.

4. In Examples 8 and 9, BHET purchased from Nanya Plastic Corporation is used.

5. The @ esterification step adds not only the Ti catalyst but also 250 ppm of Sb ₂ O ₃ catalyst. In the polymerization step only cobalt acetate (cocatalyst) is added.

Table 3. Physical Properties of PPT / PET Copolyester

Example IV -COOH Tm (℃) Tg (℃) L ^* b ^* One 0.8239 17.89 221.34 49.39 82.62 9.75 2 0.7557 12.42 190.68 54.75 78.77 5.45 3 0.7117 19.76 - 55.93 83.92 6.16 4 0.6358 10.10 - 68.89 85.73 5.39 5 0.6279 8.45 221.87 69.65 82.16 3.70 6 0.6383 17.07 239.37 72.87 82.74 3.83 7 0.6561 11.05 230 61 84.45 3.01 8 0.6773 29.16 244.86 74.32 77.96 7.77 9 0.7279 23.38 245.17 66.53 77.66 8.5 10 0.6434 26.03 241.59 67.53 74.03 5.44 11 0.6164 15.96 239.80 70.54 62.88 8.03 12 0.6325 11.26 201.36 65.59 58.58 10.31 13 0.6381 25.68 206.26 68.73 62.61 5.62 Comparative Example 1 - - - - - - Comparative Example 2 0.6383 22.61 256.29 76.03 78.73 2.15

From the above results, it can be seen that by selecting any one of the five processes of the present invention, a PPT / PET copolyester having the following characteristics can be obtained: intrinsic viscosity (IV)> 0.6 dl / g, Acid value (-COOH amont) <40 meq / kg, melting point (T _m ) = 190-250 ° C., L ^* 60, b ^* <12. In addition, in order to satisfy the requirements of suitable synthetic fibers, preferably the obtained PPT / PET copolyesters should have the following advantages of PPT: easy to dye with high elastic resilience, preferably with higher melting point and glass transition temperature than PPT. Therefore, the BHET / BHPT weight ratio is preferably controlled between 92.5 / 7.5 and 95/5.

On the other hand, preferred embodiments of the present invention described above are presented for a detailed description, it is possible to clearly modify or change as pointed out above. Selected and described embodiments are best described to best explain the principles of the present invention, and the practical application thereof employs the present invention in various modifications suitable for various embodiments and special applications implemented by those skilled in the art. Makes this possible. All such changes and modifications are intended to be included within the scope of this invention as determined by the following claims, when interpreted in accordance with a legitimately entitled claim.

According to the present invention as described above, PPT / PET copolyester can be obtained by mixing a small amount in a conventional commercial PET process to react high-priced 1,3-propanedaol with PTA, and also recently commercialized PPT / PET copolyesters can be obtained by mixing inexpensive ethylene glycol to react with PTA instead of expensive 1,3-propanediol in the PPT process.

In addition, according to the present invention, BHET, which is overproduced by a conventional commercial PET process, is used to react with PTA and 1,3-propanediol in a polymerization reaction, or BHPT produced too much in a recently commercialized PPT process. By using to react with PTA and ethylene glycol by a polymerization reaction, PPT / PET copolyester can be obtained quickly.

According to the present invention, PPT / PET copolyesters having physical properties of PPT and PET can be produced, and the obtained PPT / PET copolyesters have the following characteristics: intrinsic viscosity (IV)> 0.6 dl / g, acid value (-COOH amont) <40 meq / kg, melting point (T _m ) = 190-250 ° C., L ^* 60, b ^* <12. Furthermore, the preferred PPT / PET copolyester is 5 for the total weight of BHPT and BHET. It has a BHPT chain of -7.5 wt%.

Claims (20)

A process for producing a polypropylene terephthalate / polyethylene terephthalate (PPT / PET) copolyester comprising one process selected from the group consisting of processes (a) to (e). Here, the process (a) is carried out by esterification of bis-2-hydroxyethyl terephthalate (BHET), purified terephthalic acid (PTA) and 1,3-propanediol (1,3-PDO) to BHET and bis-2. Generating hydroxypropyl terephthalate (BHPT) and then copolymerizing BHET and BHPT; Process (b) involves esterifying PTA with 1,3-PDO to make BHPT, and adding BHET to copolymerize BHET and BHPT; Process (c) involves copolymerizing BHET and BHPT; Process (d) involves esterifying PTA, ethylene glycol (EG) and 1,3-PDO to form BHET and BHPT, and then copolymerizing BHET and BHPT; Process (e) involves esterifying BHPT, PTA and EG to produce BHPT and BHET and then copolymerizing BHET and BHPT; PPT / PET according to claim 1, wherein the purified terephthalic acid (PTA) monomers used in the processes (a), (b), (d) and (e) are of fiber grade and have the following characteristics: Copolyester Manufacturing Method: Acid value = 675 ± 2, 4CBA (4-carboxybenzaldehyde) ≤ 25 ppm, ash ≤ 15 ppm, metal ≤ 2 ppm, molecular weight = 166.13 g / mol, particle size ≤ 75 µ. The process for producing PPT / PET copolyester according to claim 1, wherein the 1,3-propanediol used in the processes (a), (b) and (d) has the following characteristics: Purity> 99%, moisture content <2 wt%. The process for producing PPT / PET copolyester according to claim 1, wherein the ethylene glycol used in the processes (d) and (e) has the following properties: Purity> 99%, moisture content <2 wt%. The process for producing PPT / PET copolyester according to claim 1, wherein in processes (a) and (b), the molar ratio of 1,3-propanediol to purified terephthalic acid is in the range of 1.3-2.4. The PPT / PET copolyester according to claim 1, wherein the bis-2-hydroxyethyl terephthalate (BHET) used in the processes (a), (b) and (c) has the following characteristics. Manufacturing Method: Acid value = 28 ± 8 KOH mg / g, saponification value = 558 ± 20 KOH mg / g, conversion ratio = 95 ± 1.5%, free ethylene glycol ≦ 4%. The process for preparing PPT / PET copolyester according to claim 1, wherein the bis-2-hydroxypropyl terephthalate (BHPT) used in the processes (c) and (e) has the following characteristics: Acid value = 3.76 ± 0.5 KOH mg / g, saponification value = 506 ± 20 KOH mg / g, conversion ratio = 98 ± 1.5%, free propylene glycol ≦ 0.046%. The process according to claim 1, wherein the esterification reactions in the processes (a), (b), (d) and (e) are 100-300 ppm (based on the weight of purified terephthalic acid) tetraethylene titanate, tetrabutylene A process for producing a PPT / PET copolyester, characterized in that it is carried out in the presence of an esterification catalyst selected from the group consisting of titanate or mixtures thereof. The PPT / PET copolyester according to claim 1, wherein the copolymerization reaction from process (a) to (e) is carried out in the presence of a polymerization catalyst selected from the group consisting of antimony acetate and antimony trioxide. Process for the preparation of esters. 10. The process of claim 9 wherein the polymerization catalysts in processes (a), (b), (d) and (e) are present in an amount of 100-300 ppm by weight of the purified terephthalic acid. Method for producing PET copolyester. The cocatalyst of claim 10, wherein the copolymerization reaction in the processes (a), (b), (d), (e) is selected from the group consisting of cobalt acetate, manganese acetate, magnesium acetate, calcium acetate, sodium acetate. Method for producing a PPT / PET copolyester characterized in that carried out in the presence of. 12. The method of claim 11, wherein the cocatalyst is present in an amount of 30-150 ppm by weight of the purified terephthalic acid. 10. The PPT of claim 9 wherein BHET in process (c) is obtained by reaction of purified terephthalic acid with ethylene glycol, and BHPT is obtained from reaction of purified terephthalic acid with 1,3-propanediol. Process for the preparation of / PET copolyester. The process of claim 13 wherein the polymerization catalyst is present in an amount of 100-300 ppm by weight of the purified terephthalic acid. 15. The PPT / PET of claim 14 wherein the copolymerization reaction in process (c) is carried out in the presence of a cocatalyst selected from the group consisting of cobalt acetate, manganese acetate, magnesium acetate, calcium acetate, sodium acetate. Method for producing copolyester. 16. The method of claim 15, wherein the cocatalyst is present in an amount of 30-150 ppm by weight of the purified terephthalic acid. The PPT according to claim 1, wherein the esterification reaction in the processes (a), (b), (d) and (e) is carried out at a temperature of 200-255 ° C and a pressure of 1-3.5 atm. Process for the preparation of / PET copolyester. The method for producing PPT / PET copolyester according to claim 1, wherein the copolymerization reaction in the processes (a) to (e) is carried out at a temperature of 240-275 ° C and a vacuum of 2.5 torr or less. The method for producing PPT / PET copolyester according to claim 1, wherein the obtained PPT / PET copolyester has the following characteristics: Intrinsic viscosity (IV)> 0.6 dl / g, acid value (-COOH amont) <40 meq / kg, melting point (T _m ) = 190-250 ° C, L ^* 60, b ^* <12. The method of claim 1 wherein the BHPT used in processes (a)-(e) is present in the range of 5-7.5 wt% based on the total weight of BHPT and BHET.