CATALYST COMPOSITION FOR A POLYESTER MANUFACTURING PROCESS

Abstract

A catalyst composition for a polyester manufacturing process, comprising a titanium catalyst and/or an antimony catalyst as main catalyst, and either (i) at least one co-catalyst A, or (ii) at least one co-catalyst Band at least one co-catalyst C, or (iii) a combination thereof, and wherein co-catalyst A is selected from the group consisting of a metal salt of an alkyl or an aryl phosphinic acid, or a metal salt of an alkyl or aryl diphosphinic acid, or a combination thereof, and co-catalyst B is selected from the group consisting of an alkyl or aryl phosphinic acid, an alkyl or aryl diphosphinic acid a combination thereof, and co-catalyst C selected from the group of a metal salt, a metal hydroxide or a metal organyl compound.

Claims

1-15. (canceled)

16. A catalyst composition for a polyester manufacturing process, comprising a titanium catalyst and/or an antimony catalyst as a main catalyst, and either (i) at least one co-catalyst A, or (ii) at least one co-catalyst B and at least one co-catalyst C, or (iii) a combination of at least one co-catalyst A, at least one co-catalyst B and at least one co-catalyst C, and wherein the co-catalyst A is selected from the group consisting of a metal salt of an alkyl or an aryl phosphinic acid, or a metal salt of an alkyl or aryl diphosphinic acid and a combination thereof, and the co-catalyst B is selected from the group consisting of an alkyl or aryl phosphinic acid, an alkyl or aryl diphosphinic acid and a combination thereof, and the co-catalyst C is selected from the group consisting of a metal salt, a metal hydroxide and a metal organyl compound.

17. The catalyst composition according to claim 16, comprising a titanium catalyst and/or an antimony catalyst as the main catalyst, the at least one co-catalyst A, and optionally the co-catalyst C.

18. The catalyst composition according to claim 16, wherein the co-catalyst A is selected from the group consisting of compounds of formula (I) and (II) ##STR00004## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are each independently from each other a linear or branched, saturated or unsaturated C.sub.1 to C.sub.6 alkyl and/or or an aryl residue residues and are the same or different from each other, and R.sub.5 is a C.sub.1 to C.sub.12 a linear or branched, saturated or unsaturated alkylene, a C.sub.6 to C.sub.18 arylene, a C.sub.6 to C.sub.18 alkyl arylene or a C.sub.6 to C.sub.18 arylalkylene, M is selected from the group consisting of aluminum, cobalt and zinc ions, m is 2, 3 or 4, and n is 1 or 2.

19. The catalyst composition according to claim 16, wherein the co-catalyst B is selected from the group consisting of compounds of formula (III) and (IV) ##STR00005## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are each independently from each other a linear or branched, saturated or unsaturated C.sub.1 to C.sub.6 alkyl and/or or an aryl residue residues and are the same or different from each other, and R.sub.5 is a linear or branched, saturated or unsaturated C.sub.1 to C.sub.12 alkylene, a C.sub.6 to C.sub.18 arylene, a C.sub.6 to C.sub.18 alkyl arylene or a C.sub.6 to C.sub.18 arylalkylene.

20. The catalyst composition according to claim 16, wherein the co-catalyst C is selected from the group consisting of zinc acetate, zinc chloride, zinc nitrate, zinc sulfate, aluminum chloride, aluminum hydroxide, aluminum acetate, aluminum hydroxychloride, cobalt acetate, cobalt nitrate, cobalt chloride, cobalt acetylacetonate, cobalt naphthenate, cobalt hydroxide, cobalt salicate, and combinations thereof.

21. The catalyst composition according to claim 18, wherein the co-catalyst B is selected from the group consisting of compounds of formula (III) and (IV) ##STR00006## wherein R.sub.5 is a linear or branched, saturated or unsaturated C.sub.1 to C.sub.12 alkylene, a C.sub.6 to C.sub.18 arylene, a C.sub.6 to C.sub.18 alkyl arylene or a C.sub.6 to C.sub.18 arylalkylene, and wherein in the compounds of formula (I), (II), (III) and (IV) R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are each independently from each other a linear or branched saturated or unsaturated C.sub.1 to C.sub.6 alkyl residue residues or a phenyl and are the same or different from each other.

22. The catalyst composition according to claim 21, wherein in the compounds of formula (I), (II), (III) and (IV) R.sub.1 and R.sub.2 are each independently from each other methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl and/or or phenyl.

23. The catalyst composition according to claim 18, wherein the co-catalyst B is selected from the group consisting of compounds of formula (III) and (IV) ##STR00007## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are each independently from each other a linear or branched, saturated or unsaturated C.sub.1 to C.sub.6 alkyl and/or or an aryl residue residues and are the same or different from each other, and wherein in the compounds of formula (II) and (IV) R.sub.5 is selected from the group consisting of methylene, ethylene, n-propylene, isopropylene, n-butylene, tert-butylene, n-pentylene, n-octylene, n-dodecylene, phenylene, methylphenylene, ethylphenylene, tert-butylphenylene, methylnaphthylene, ethylnaphtylene, tert-butylnaphthylene, phenylmethylene, phenylethylene and phenylbutylene.

24. The catalyst composition according to claim 16, wherein the co-catalyst A is zinc diethylphosphinate.

25. The catalyst composition according to claim 16, wherein the catalyst system consists of a titanium catalyst as the main catalyst, the at least one co-catalyst B, and the at least one co-catalyst C, wherein the co-catalyst C is selected from the group consisting of cobalt acetate, cobalt nitrate, cobalt chloride, cobalt acetylacetonate, cobalt naphthenate, cobalt hydroxide, cobalt salicate.

26. A process of manufacturing a polyester, the process comprising: preparing a polyester in the presence of the catalyst composition according to claim 1.

27. The process of claim 26, wherein the polyester manufacturing process occurs in the absence of a carboxy compound as a starting compound.

28. The process of claim 26, further comprising: esterifying a carboxy compound with an alcohol to obtain an esterified mixture; and polymerizing the esterified mixture at temperatures in the range of 260° C. to 300° C. to obtain the polyester.

29. A polyester manufactured with the catalyst composition according to claim 16.

30. The polyester of claim 29, wherein the polyester is a polyethylene terephthalate.

Description

EXPERIMENTAL PART

Reaction Conditions and Analytical Evaluation of the Polyesters

[0079] The polycondensation progress is controlled by measuring of differential torque value (ΔC) of the mixing device. This parameter depends on the viscosity change of reaction mixture. For every PET synthesized, ΔC is set to 15 Nm as a typical value for PET with a reduced viscosity between 70-78 mL/g. Once this value is attained, the reactor is opened and the polymer collected. The time of beginning of polycondensation (t0=0 min) is taken when the reactor pressure reaches 20 mbar.

[0080] Three experimental techniques are used to determine properties of PET obtained during this study.

[0081] 1. Capillary Viscosimetry Analysis (Method ASTM D4603).

[0082] This technique allows the measurement of the intrinsic viscosity of PET in solution from the study of the flow time of pure solvent (t0) and of polymer solution (t). Different data characterizing the polymer viscosity can be calculated by this method:

Relative viscosity.fwdarw.ηrel=t/t0

Specific viscosity.fwdarw.ηsp=(t−t0)/t0

Reduced viscosity.fwdarw.ηred=(t−t0)/C*t0

[0083] In the literature, people skilled in the art have managed to establish a model to deduce directly from these expressions of viscosity: the intrinsic viscosity ([η]), number average molar mass and weight average molar mass (Mn, Mw) and the average degrees of polymerization DPn. We used two models for PET on the range of reduced viscosity: 5 ml/g<ηred<100 mL/g. One model to calculation for intrinsic viscosity is:

[00001]$\left[\eta \right]=\frac{\sqrt{2\times \left({\eta }_{sp}-Ln{\eta }_{rel}\right)}}{C}$

[0084] The other model was developed for the determination of molar mass of PET, with the following equations:

M.sub.n=228.9×η.sub.red−1333

M.sub.w=613.2×η.sub.red−3753.4

DP.sub.n=1.19×η.sub.red−6.97

[0085] 2. Differential Scanning Calorimetry Analysis (DSC)

[0086] DSC is a thermal analysis of the obtained polymer. t allows to determine the melting, crystallization and glass transition temperature. The temperature program has a first temperature ramp (from 35 to 275° C.) with a heating rate of 10° C./min, a cooling step at 10° C./min and a second heating ramp at 10° C./min. The analysis is run under nitrogen. From the first heating ramp we determine: the cold-crystallization temperature (Tc1), crystallization enthalpie (ΔHc1), melting temperature (Tm1) and melting enthalpy (ΔHm1). The degree of crystallization (χc1) is calculated using the following equation:

[00002]${\varkappa }_{c1}=\frac{\Delta H_{m1}-\Delta H_{c1}}{\Delta H_0}\times 100$

ΔH0: melting enthalpy of pure single crystal of PET (117.6 J/g)

[0087] From the cooling ramp we find the melt-crystallization temperature (Tc2) and crystallization enthalpy (ΔHc2). From the second heating ramp we determine: the glass transition temperature (Tg3), the cold-crystallization temperature (Tc3), crystallization enthalpy (ΔHc3), the degree of crystallinity (χc3), melting temperature (Tm3), and melting enthalpy (ΔHm3).

[00003]${\varkappa }_{c3}=\frac{\Delta H_{m3}-\Delta H_{c3}}{\Delta H_0}\times 100$

[0088] 3. Nuclear Magnetic Resonance Spectroscopy (NMR)

[0089] 1H-NMR is used to quantify the amount of diethylene glycol (so called DEG) in the chain. The DEG is formed during the synthesis by an etherification reaction. It is very important to measure the rate of DEG because it can influence the mechanical and thermal properties of PET. A large amount of DEG can reduce the glass transition temperature, melting temperature and the crystallization rate.

[0090] All analyzes are performed in a solvent mixture of deuterated chloroform (CDCl3)/trifluoroacetic acid (TFA) (3/1) (V/V)

[0091] The DEG rate (RDEG) is calculated from the integration of area proton peaks for different forms of DEG in the macromolecular PET chain appearing in between 4 ppm and 5 ppm.

[00004]${\mathrm{Rate}}_{DEG}=\frac{I_c}{I_b+I_c+I_e+I_f}\times 100$

[0092] Experimental Results

[0093] The reactor can synthesize around 3 kilograms (3072 g theoretical amount, 16 moles of PET) of polymer for each run (batch), all PETs are synthesized from 16 mol of terephthalic acid (TA) and 19.2 mol of ethylene glycol (EG) monomers that are used in the PET industry. The catalysts based on titanium and antimony, the phosphorus additives and color correction based metal salts were used in the formulation of PET. All products, their chemical structure, properties and quantity were determined by appropriate analytical methods.

[0094] Catalyst Mixture Preparation

[0095] The different components (1), (2), (3) and (4) of the catalytical system can be added separately during the polymerization process or ready-to-use mixtures can be prepared in advance by mixing the constituents following a given ratio in a solvent. This solution is then introduced to the process in the direct esterification or the polycondensation steps.

[0096] Typical quantities used per batch in polymerization for each individual component (Monomers (M) and catalysis formulations)

TABLE-US-00001 Amount used Type Products per batch M Terephthalic acid   16 mol. M Ethylene glycol 19.2 mol. 1 Tetrabutyl titanate 7 ppm Ti 1 Antimony acetate 250 ppm Sb 1 Antimony trioxide 250 ppm Sb 2 diethylphosphinic acid-(DEPS) 5 ppm P 2 Aluminum (III) diethylphosphinate-(Al(DEP)3) 5 ppm P 2 Ethylen-1,2-bis(ethylphosphinic acid)-(DiPOS) 5 ppm P 3 Cobalt (II) acetate tetrahydrate 25 ppm Co 3 Zinc (II) acetate 56 ppm Zn 3 Zinc (II) diethylphosphinate (Zn(DEP)2) 56 ppm Zn 4 Ethylene glycol

##STR00003##

[0097] Example of Catalyst Mixture Preparation:

[0098] In a typical titanium based catalyst preparation, 0.15 grams of Ti(OBu).sub.4, 0.32 grams of Cobalt acetate tetrahydrate and 0.06 grams of diethylphosphinic acid (DEPS) are diluted into 10 ml of ethylene glycol. The transparent violet solution is stirred for 90 minutes at room temperature and used as catalyst for the example 4 (table 1).

[0099] An equivalent formulation is stored for one additional week and evaluate in another polymerization trial. The aged solution is shown to perform similarly to the freshly prepared one.

[0100] In a typical antimony based catalyst preparation, 0.92 grams of Sb(OAc).sub.3, 0.32 grams of Cobalt acetate tetrahydrate and 0.05 grams of diethylphosphinic acid (DEPS) are diluted into 10 ml of ethylene glycol. The transparent violet solution is stirred for 90 minutes at room temperature and used as catalyst for the example 19 (table 3).

[0101] An equivalent formulation is stored for one additional week and evaluate in another polymerization trial. The aged solution is shown to perform similarly to the freshly prepared one.

[0102] Direct Esterification Step

[0103] 16 mol (2656 g) of Terephthalic acid (AT) is esterified with 19.2 mol of ethylene glycol EG (1190 g) under a nitrogen pressure of 6.6 bar and a temperature of 275° C. The molar ratio EG/AT is equal to 1,2. The catalysts and the cocatalysts or the ready-to-use mixture in ethylene glycol are introduced by an adapted device to the reactor. The agitator was turned on and the temperature increased to 275° C. over a period of about 2.5 hours. The contents were esterified by holding under agitation at 275° C. and a pressure of 120 mm Hg, and at 280° C. and a pressure of 30 mm Hg.

[0104] The progress of the reaction is controlled by the amount of water recovered named the “conversion”. When the direct esterification step was completed (no water distilled off), the polycondensation step is started.

[0105] Polycondensation Step

[0106] The polycondensation step consists of coupling the PET oligomers formed during the esterification step, by transesterification reactions (also referred as exchange reactions) alcohol-ester which lead to release the excess of ethylene glycol molecules. The reaction takes place at 285° C. under reduced pressure of 0.7 mbar. The contents of the kettle were held under agitation at 285° C. at 1 to 2 mm Hg pressure for a time sufficient to reach 15 ounce-inch (0.106 Newton-meter) torque as measured by an Electro-Craft Motomatic torque controller. The time for this step was recorded as the Finish Time, and varied with the catalyst system used. The polymer melt was then poured into a water bath to solidify the melt, and the resultant solid annealed at 0° C. for 12 hours and ground to pass through a 2 mm filter for color measurements using a spectrophotometer.

[0107] Results

TABLE-US-00002 TABLE 1 Polymerisation results with titanium based catalysts (1a and 1b being the references) (Ti) (P) (M) Example “(1)” ppm IS “(2)” ppm “(3)” (ppm) IS t1 t2 t1 + t2 Δ  1a Ti(OBu).sub.4 7 2 none 0 none  0 — 105 76 181   0  1b Ti(OBu).sub.4 7 1 none 0 none  0 — 90 80 170 −11  2 Ti(OBu).sub.4 7 2 DEPS 5 Co(OAc).sub.2 25 1 95 52 147 −34  3 Ti(OBu).sub.4 7 2 DiPOS 5 Co(OAc).sub.2 25 1 90 60 150 −31  4 Ti(OBu).sub.4 7 1 DEPS 5 Co(OAc).sub.2 25 1 85 52 137 −44  5 Ti(OBu).sub.4 7 1 DEPS 10 Co(OAc).sub.2 25 1 85 61 146 −35  6 Ti(OBu).sub.4 7 1 DEPS 2.5 Co(OAc).sub.2 25 1 85 54 139 −42  7 Ti(OBu).sub.4 7 1 Di POS 5 Co(OAc).sub.2 25 1 85 61 146 −35  8 Ti(OBu).sub.4 7 1 DiPOS 2.5 Co(OAc).sub.2 25 1 90 61 151 −30  9 Ti(OBu).sub.4 7 2 DEPS 5 Co(OAc).sub.2 25 1 90 50 140 −41 10 Ti(OBu).sub.4 7 1 Al(DEP)3 5 Co(OAc).sub.2 25 1 95 52 147 −34 11 Ti(OBu).sub.4 7 1 DEPS 5 Zn(OAc).sub.2 56 1 90 37 127 −54 12 Ti(OBu).sub.4 7 1 DEPS 5 Co(OAc).sub.2 25 1 85 51 136 −45 13 Ti(OBu).sub.4 7 1 DiPOS 5 Zn(OAc).sub.2 56 1 90 37 127 −54 14 Ti(OBu).sub.4 7 2 DEPS 5 Zn(OAc).sub.2 56 1 90 37 127 −54 15 Ti(OBu).sub.4 7 2 DiPOS 5 Zn(OAc).sub.2 56 1 85 39 124 −57 16 Ti(OBu).sub.4 7 1 none 0 Zn(OAc).sub.2 56 — 85 43 128 −53 Abreviations- IS: introduction step of the ingredients. IS 1: co-catalyst introduced at DE step. IS 2: main catalyst introduced at PC step. DE: direct esterification. PC: polycondensation. t1: DE time/min. t2: PC time/min

TABLE-US-00003 TABLE 2 Qualitiative color measurement (1a and 1b being the references) (Ti) PET Example “(1)” ppm IS “(2)” (P) ppm “(3)” (M) ppm IS color 1a Ti(OBu).sub.4 7 2 none 0 none 0 — yellow 1b Ti(OBu).sub.4 7 1 none 0 none 0 — yellow  2 Ti(OBu).sub.4 7 2 DEPS 5 Co(OAc).sub.2 25 1 Light yellow  3 Ti(OBu).sub.4 7 2 DiPOS 5 Co(OAc).sub.2 25 1 Light yellow  4 Ti(OBu).sub.4 7 1 DEPS 5 Co(OAc).sub.2 25 1 Light yellow  5 Ti(OBu).sub.4 7 1 DEPS 10 Co(OAc).sub.2 25 1 Light yellow  6 Ti(OBu).sub.4 7 1 DEPS 2.5 Co(OAc).sub.2 25 1 Light yellow  7 Ti(OBu).sub.4 7 1 DiPOS 5 Co(OAc).sub.2 25 1 Light yellow  8 Ti(OBu).sub.4 7 1 DiPOS 2.5 Co(OAc).sub.2 25 1 Light yellow  9 Ti(OBu).sub.4 7 2 DEPS 5 Co(OAc).sub.2 25 1 Light yellow 10 Ti(OBu).sub.4 7 1 Al(DEP)3 5 Co(OAc).sub.2 25 1 Light yellow 11 Ti(OBu).sub.4 7 1 DEPS 5 Zn(OAc).sub.2 56 1 grey 12 Ti(OBu).sub.4 7 1 DEPS 5 Co(OAc).sub.2 25 1 Light yellow 13 Ti(OBu).sub.4 7 1 DiPOS 5 Zn(OAc).sub.2 56 1 grey 14 Ti(OBu).sub.4 7 2 DEPS 5 Zn(OAc).sub.2 56 1 grey 15 Ti(OBu).sub.4 7 2 DiPOS 5 Zn(OAc).sub.2 56 1 grey 16 Ti(OBu).sub.4 7 1 none 0 Zn(OAc).sub.2 56 1 Light grey Abreviations- IS: introduction step of the ingredients. IS 1: co-catalyst introduced at DE step. IS 2: main catalyst introduced at PC step. DE: direct esterification. PC: polycondensation

TABLE-US-00004 TABLE 3 Polymerisation results with antimony based catalysts (17a and 17b being the references) Ex- (M) ample “(1)” (Sb) ppm IS “(2)” (P) ppm “(3)” ppm IS t1 t2 t1 + t2 Δ 17a Sb.sub.2O.sub.3 200 1 none 0 none 0 90 80 170 −19 17b Sb.sub.2O.sub.3 200 2 none 0 none 0 1 105 84 189 0 18 Sb.sub.2O.sub.3 200 2 DEPS 5 Co(OAc).sub.2 25 1 100 55 155 −34 19 Sb.sub.2O.sub.3 200 1 DEPS 5 Co(OAc).sub.2 25 1 85 63 148 −41 20 Sb.sub.2O.sub.3 200 1 DiPOS 5 Co(OAc).sub.2 25 1 90 67 157 −32 23 Sb.sub.2O.sub.3 200 1 Al(DEP)3 5 Co(OAc).sub.2 25 1 90 62 152 −37 24 Sb(OAc).sub.3 200 1 none 0 Zn(DEP).sub.2 56 1 85 45 130 −59 Abreviations- IS: introduction step of the ingredients. IS 1: co-catalyst introduced at DE step. IS 2: main catalyst introduced at PC step. DE: direct esterification. PC: polycondensation. t1: DE time/min. t2: PC time/min

TABLE-US-00005 TABLE 4 Qualitative color measurement (17a and 17b being the references) (Sb) (P) (M) Example “(1)” ppm IS “(2)” ppm “(3)” ppm IS color 17a Sb.sub.2O.sub.3 200 1 none 0 none 0 Light yellow 17b Sb.sub.2O.sub.3 200 2 none 0 none 0 Light yellow 18 Sb.sub.2O.sub.3 200 2 DEPS 5 Co(OAc).sub.2 25 1 Light yellow 19 Sb.sub.2O.sub.3 200 1 DEPS 5 Co(OAc).sub.2 25 1 Light yellow 20 Sb.sub.2O.sub.3 200 1 DiPOS 5 Co(OAc).sub.2 25 1 Light grey 21 Sb.sub.2O.sub.3 200 1 Al(DEP).sub.3 5 none 0 Light grey 22 Sb(OAc).sub.3 200 1 Al(DEP).sub.3 5 none 0 Light yellow 23 Sb.sub.2O.sub.3 200 1 Al(DEP).sub.3 5 Co(OAc).sub.2 25 1 Light grey 24 Sb(OAc).sub.3 200 1 none 0 Zn(DEP).sub.2 56 1 white Abreviations- IS: introduction step of the ingredients. IS 1: co-catalyst introduced at DE step. IS 2: main catalyst introduced at PC step. DE: direct esterification. PC: polycondensation

TABLE-US-00006 TABLE 5 Thermal and crystallization properties of PET synthesized with the new catalysts mixtures-DEG content measurements in %. T.sub.c1, T.sub.m1, T.sub.c2, T.sub.c3, T.sub.m3, Ex- ΔH.sub.c1 ΔH.sub.m1 ΔH.sub.c2 ΔH.sub.c3 ΔH.sub.m3 am- (° C., (° C., X.sub.c1 (° C., (° C., (° C., X.sub.c3 R.sub.DEG ple J .Math. g.sup.−1) J .Math. g.sup.−1) (%) J .Math. g.sup.−1) J .Math. g.sup.−1) J .Math. g.sup.−1) (%) (%)  1a 142/33 244/39 5.1 148/26 147/5  243/37 27 6.6  1b 145/37 245/40 2.5 148/26 149/11 244/38 23 6.2  2 142/34 247/40 5.1 145/18 146/12 246/37 21 5.3  4 145/37 248/43 5.1 156/34 149/6  247/40 29 5  6 144/33 249/39 5.1 152/25 148/7  247/36 24 4.8  5 142/35 249/39 3.4 150/23 147/9  246/35 22 5  3 140/37 247/43 5.1 154/34 148/7  246/41 29 5.2  7 143/33 249/38 4.2 156/28 146/7  248/35 24 4.8 16 143/36 249/42 5.1 156/24 149/13 248/40 23 4.9 24 133/34 249/42 6.8 181/42 ND*/0 248/39 33 4.9

[0108] Comparison examples: Polyesterification experiments of Ref 1 to 4 are conducted only with main catalysts. These catalysts were introduced either in the step 1 or the step 2. Ref 5 to 13 are conducted with a phosphorus source. The phosphorus source can be a phosphinite like Hostanox P-EPQ (PEPQ) or a phosphite like Irganox 168 (IRG 168). Carboxyethyl phosphinic acid (CEPA) was also evaluated. As described in the following table, the full reaction time improvements (sum) are quite limited.

TABLE-US-00007 Ex- DE PC Sum ample catalyst IS Phosphorus IS (Min) (Min) (Min) ref 1 Ti(OBu).sub.4 1 none “−” 90 80 170 ref 2 Sb.sub.2O.sub.3 1 none “−” 90 80 170 ref 3 Ti(OBu).sub.4 2 none “−” 105 76 181 ref 4 Sb.sub.2O.sub.3 2 none “−” 105 84 189 ref 5 Ti(OBu).sub.4 2 P-EPQ 1 100 113 213 ref 6 Ti(OBu).sub.4 2 CEPA 1 95 89 184 ref 7 Sb.sub.2O.sub.3 2 P-EPQ 1 100 89 189 ref 8 Sb.sub.2O.sub.3 2 CEPA 1 95 90 185 ref 9 Ti(OBu).sub.4 1 P-EPQ 1 90 113 203 ref 10 Ti(OBu).sub.4 2 CEPA 2 95 67 162 ref 11 Ti(OBu).sub.4 2 P-EPQ 2 100 77 177 ref 12 Ti(OBu).sub.4 2 IRG 168 2 105 71 176 ref 13 Ti(OBu).sub.4 2 IRG 168 1 97 87 184

[0109] Comparison examples: Polyesterification experiments of Ref 14 to 20 are conducted with reported cocatalysts (Zn and Co acetates). These cocatalysts were introduced either in the step 1 or the step 2. As described in the following table, the full reaction time is improved especially for the Zinc cocatalyst but the overall quality of the obtained polyester is rather poor (severe yellowing and low viscosity).

TABLE-US-00008 DE PC Sum Example catalyst IS Phosphorus IS (Min) (Min) (Min) Ref 14 Sb.sub.2O.sub.3 2 Co(OAc).sub.2 1 100 58 158 Ref 15 Ti(OBu).sub.4 2 Co(OAc).sub.2 1 100 57 157 Ref 16 Ti(OBu).sub.4 1 Co(OAc).sub.2 1 85 58 143 Ref 17 Sb.sub.2O.sub.3 1 Co(OAc).sub.2 1 95 60 155 Ref 18 Ti(OBu).sub.4 1 Zn(OAc).sub.2 1 90 56 146 Ref 19 Sb.sub.2O.sub.3 1 Zn(OAc).sub.2 1 90 50 140 Ref 20 Ti(OBu).sub.4 2 Zn(OAc).sub.2 1 90 52 142