GB1569799A - Preparation of poly(ethylene terephthalate)using catalyst composition - Google Patents

Description

(54) PREPARATION OF POLY (ETHYLENE TEREPHTHALATE) USING IMPROVED CATALYST COMPOSITION (71) We, EASTMAN KODAK COMPANY, a Company organized under the Laws of the State of New Jersey, United States of America of 343 State Street, Rochester New York 14650, United States of America do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to the preparation of poly(ethylene terephthalate), and to a catalyst composition for use in such preparation. This invention is an improvement in or modification of the invention claimed in our Patent No.

1,522,656.

Poly(ethylene terephthalate) may be prepared by carrying out an ester interchange between ethylene glycol and dimethyl terephthalate to form bis-2hydroxy ethyl terephthalate, which is polycondensed to poly(ethylene terephthalate) under reduced pressure and at elevated temperatures.

Difficulties have been encountered in the manufacture of poly(ethylene terephthalate) by the ester interchange reaction. While highly purified dimethyl terephthalate and ethylene glycol are preferred starting materials in order to form a uniform high quality product, even these highly purified materials are very sluggish with respect to ester interchange, and in the case of less purified materials the reaction is too slow for practical commercial operation. Because of this slow rate of reaction it has been found essential, in commercial operation, to employ a suitable catalyst to speed up the reaction.

Many catalysts have been proposed for the ester interchange reaction in the manufacture of poly(ethylene terephthalate), but have not been found to be entirely satisfactory since fibres and filaments produced from the condensation polymers using such known catalysts do not possess the desired whiteness or lack of colour. Furthermore, when fabrics prepared from some polyesters are dyed with certain dyes, such as metallized anthraquinones, the dyes undergo a bathochromic shift during dyeing or during subsequent yarn or fabric treatment, leading to dull undesirable colours, particularly when dyeing to pastel shades. Examples of dyes that are particularly adversely affected are C.I. Disperse Red 91, C.l. Disperse Blue 27, and C.l. Disperse Red 60. Many other hydroxy or amino anthraquinone dyes will also undergo a colour shift when used to dye such polyester yarns or fabrics. It is believed that any dye containing active hydrogens will undergo this reaction to some degree.

This invention overcomes deficiencies in prior art catalyst compositions while facilitating the preparation of poly (ethylene terephthalate) at a high production rate, the product having good colour and excellent stability against thermooxidative, hydrolytic and ultraviolet radiation degradation effects.

Claim 1 of Patent No. 1 522 656 is as follows: A process for producing polytethylene terephthalate) wherein dimethyl terephthalate and ethylene glycol are reacted at a temperature sufficient to effect ester interchange and in the presence of a catalytic amount of a catalyst comprising a mixture of organic or inorganic salts of manganese and cobalt with a titanium alkoxide and an organic salt of an alkali metal or an alkaline earth metal, and the ester reaction product of the ester interchange is polycondensed.

According to the present invention, there is provided a process for producing poly(ethylene terephthalate) wherein dimethyl terephthalate and ethylene glycol are reacted at a temperature sufficient to effect ester interchange and in the presence of a catalytic amount of a catalyst comprising a mixture of organic or inorganic salts of manganese and cobalt with a titanium alkoxide and antimony or an antimony compound, and the ester reaction product of the ester interchange is polycondensed.

Claim 19 of Patent No. 1 522 656 is as follows: A catalyst composition comprising a mixture of organic or inorganic salts of manganese and cobalt with a titanium alkoxide and an organic salt of an alkali metal or an alkaline earth metal.

Also according to the present invention, there is provided a catalyst composition comprising a mixture of organic or inorganic salts of manganese and cobalt with a titanium alkoxide and antimony or an antimony compound.

Examples of suitable manganese salts are manganous benzoate tetrahydrate, manganese chloride, manganese oxide manganese acetate, manganese acetylacetonate, manganese succinate, manganese diethyldithiocarbamate, manganese antimonate, manganic phosphate monohydrate, manganese glycoxide, manganese naphthenate, and manganese salicyl salicylate.

Examples of suitable cobalt salts are cobaltous acetate tetrahydrate, cobaltous nitrate, cobaltous chloride, cobalt acetylacetonate, cobalt naphthenate, and cobalt salicyl salicylate.

Examples of suitable titanium alkoxides are acetyl triisopropyl titanate, titanium tetraisopropoxide, titanium glycolates, titanium butoxide, hexylene glycol titanate, and tetraisooctyl titanate. The alkoxide radicals in the titanium alkoxides usually contain 1 to 8 carbon atoms.

Examples of some suitable antimony compounds which, as alternatives to antimony metal and metal alloys, are useful in this invention are antimony III and V halides, hydroxides and sulphides; antimony III, IV and V oxides; antimony salts of carboxylic acids such as the acetate, lactate, oxalate, phthalate, benzoate, or mixtures thereof; antimony III and V glycolates; and antimony alcoholates such as

where R1, R2 and R3 are alkyl or cycloalkyl radicals which may include inert substituents. When R1, R2, or R3 is alkyl, it may be straight chain or branched, for example a methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-amyl, neopentyl, isoamyl, n-hexyl, isohexyl, heptyl, octyl, decyl, dodecyl, tetradecyl or octadecyl radical. Preferred alkyl radicals are those containing less than 8 carbon atoms. When R1, R2 or R3 is cycloalkyl, it may, for example, be a cyclopentyl, cyclohexyl, cycloheptyl or cyclooctyl radical. Examples of inert substituents in R1, R2 or R3 are alkoxy, halogen, nitro and ester groups. Typical substituted alkyl radicals are 3-chloropropyl, 2-ethoxyethyl and carboethoxymethyl radicals Examples of substituted cycloalkyl radicals are 4-methylcyclohexyl and 4chlorocyclohexyl radicals.

Alkyl antimonites such as phenyl, tolyl, or butyl antimonites; metal antimonates such as magnesium antimonate or sodium antimonate; and divalent metal antimonites such as magnesium, manganese, zinc, calcium or cobalt antimonites are also useful.

In the preparation of poly(ethylene terephthalate) in accordance with the invention, the process can be considered as comprising two steps. In the first step, ethylene glycol and dimethyl terephthalate are reacted at elevated temperatures and atmospheric pressure to form bis-2-hydroxyethyl terephthalate (BHET) and methanol, the methanol being removed. Thereafter the BHET is heated under still higher temperatures and under reduced pressure to form poly(ethylene terephthalate) with the elimination of glycol, which is readily volatilized under these conditions and removed from the system. The second step, or polycondensation step, is continued until a fibre-forming polymer having the desired degree of polymerization, determined by inherent viscosity, is obtained.

Without the aid of a suitable catalyst, the above reactions do not proceed at a. noticeable rate.

Inherent viscosity for the poly(ethylene terephthalate) prepared in accordance with the invention is determined by measuring the flow time of a solution of known polymer concentration and the flow time of the polymer solvent in a capillary viscometer with a 0.55 mm. capillary and a 0.5 ml. bulb having a flow time of 100 + 15 seconds and then by calculating the inherent viscosity using the equation: In ts 250C Inherent Viscosity (I.V.), n 0.50% PTCE = to C where: 1 a = Natural logarithm t, = Sample flow time to = Solvent blank flow time C = Concentration in grams per 100 ml. of solvent PTCE = 60% phenol, 40% tetrachloroethane The basic method is set forth in ASTM D2857-70.

The method used for calculating catalyst metal concentrations in poly(ethylene terephthalate) for purposes of this specification may be illustrated as follows. The poly(ethylene terephthalate) is prepared in 0.60 gram mole batches.

The repeat unit empirical formula of the polymer is C,0HaO4, and its gram molecular weight is thus 192.16 g. A 0.60 mole batch is therefore 115.30 g. A 0.60 mole batch of polymer requires 0.60 mole of terephthalic acid or its alkyl esters such as dimethyl terephthalate (DMT;mol. wt. = 194.19). Thus, 0.60 mole of this "acid fraction" as DMT is: 0.60 mole x 194.19g./mole = 116.51 g. Catalyst metals levels are stated in parts by weight of metal per million parts by weight of DMT. Thus, 48 ppm Ti is.

194.19 g./mole 0.60 mole x x 48 = 0.00559267 g. Ti 1,000,000 The weights of other catalyst metals or other additives are calculated similarly.

The manganese salt is preferably present in the amount of 25-110 parts per million manganese; the cobalt salt is preferably present in the amount of 10100 parts per million cobalt; the titanium alkoxide is preferably present in the amount of 2060 parts per million titanium and the antimony or antimony compound is preferably present in an amount of 50300 ppm. of antimony. All parts by weight are based on the acid fraction of the polymer to be produced.

The preferred manganese salt is manganous benzoate tetrahydrate and the preferred cobalt salt is cobaltous acetate tetrahydrate. The preferred antimony compound is antimony triacetate.

A phosphate ester is preferably used in the reaction mixture during the process of the invention. The phosphate ester is typically present during the polycondensation step. Phosphate esters function as colour stabilizers for the poly(ethylene terephthalate) prepared in accordance with the invention. The preferred phosphate ester that can be used in the invention has the formula

wherein n has an average value of 1.5 to 3.0, with 1.8 being most preferred, and each R is hydrogen or an alkyl radical having from 6to 10 carbon atoms, with octyl being most preferred. The ratio of the number of acidic hydrogen atoms represented by R to the number of phosphorus atoms is generally 0.25 to 0.50, with 0.35 being most preferred. The ester generally has a free acidity equivalent of 0.2 to 0.5 and is generally present in an amount that provides 13-240 parts jeer million phosphorus based on the acid fraction of the polyester to be produced.

A particularly useful phosphate ester of this preferred type has a molecular weight of 771 and has the composition: C = 52.84 ,, H = 9.98 /; P = 8.040:, and 0 = 29.14% by weight.This ester is referred to hereinafter as "Phosphate Ester A".

Other useful phosphate esters include ethyl dihydrogen phosphate, diethyl hydrogen phosphate, triethyl phosphate, aryl alkyl phosphates, and tris-2ethylhexyl phosphate.

The phosphate ester may be used in an amount to provide phosphorus at a concentration such that the atom ratio of the amount of phosphorus to the sum of the amounts of cobalt, manganese, and titanium is between 1.0 and 2.0, i.e., [P] 1.0 < < 2.0 [Mn] + [Co] + [Ti] where [] in each case refers to the number of gram atoms of respective components. (Gram atoms of any element = weight of the element in grams divided by the atomic weight of the element in grams.) The process and catalyst composition of this invention provide for the manufacture at high production rates of high quality poly(ethylene terephthalate) polyester having excellent properties for the fabrication of fibres and films.

Poly(ethylene terephthalate) produced in accordance with this invention has excellent colour (whiteness), low concentration of diethylene glycol (ether linkages), excellent stability against thermooxidative, hydrolytic, and ultraviolet radiation degradation effects, and when melt spun into fibres or filaments leaves essentially no deposits on spinneret faces.

The data set forth in the following examples illustrate these effects. Examples 13 and 26 are examples of the invention. The data in Table 1 illustrate that the catalyst compositions of the invention are as useful as other catalysts with respect to the colour of polyester prepared, and the data in Table 2 illustrate that the catalyst compositions of the invention have the added advantage of yielding polyesters having improved thermooxidative stability. The data in Table 3 illustrate that the bathochromic shift of dyes used in subsequent dyeing can be controlled when the catalyst compositions of the invention are used. The data in Example 27 show the increased average polycondensation rate that is obtained with the catalyst compositions of this invention.

TABLE 1 Properties of Poly(ethylene terephthalate) made with Various Catalyst Compositions Example Catalyst Compositions (ppm) I.V. % DEG CEG4 CDM Colour5 1 (65)Zn-(230)Sb-(31)P .60 1.08 29 1.9 2 *(48)Ti-(62)P .72 1.30 25 4.9 3 (12)Mg-(48)Ti-(62)P .72 0.67 17 5.2 4 **(48)Ti-(62)P .62 1.18 20 4 7 5 (236)Mn-(374)Sb-(44)P .64 0.70 24 5.1 6 **(50)Mn-(48)Ti-(50)P .71 0.62 13 6.5 7 **(50)Mn-(60)Ti-(20)Co-(80)P .58 0.52 8 3.1 8 **(70)Mn-(60)Ti-(20)Co-(80)P .61 0.50 20 2.6 9 **(76)Mn-(48)Ti-(13)Co-(17)Li-(74)P .61 1.00 26 4.5 10 **(63)Mn-(58)Ti-(13)Co-(28)Li-(98)P .61 1.20 18 1.3 11 **(21)Ti-(40Mn-(10)Co-(16)Li-(75)P .61 0.92 17 -0.9 12 **(25)Ti-(44)Mn-(15)Co-(19)Li-(97)P .63 0.87 12 -0.8 13 **(29)Mn-(44)Ti-(13)Co-(72)Sb-(75)P .63 1.02 21 -0.5 * Ti as titanium tetraisopropoxide.

** Ti as acetyl triisopropyl titanate.

1 ppm by weight of metal based on polyester acid fraction.

2 Inherent viscosity of 0.5 g./100 ml of 60/40 (w/w) phenol/tetrachloroethane &commat; 25 C.

3 Diethylene glycol, wt. percent.

4 Carboxyl end groups, milliequivalents/Kg.

5 Yellowness value determined by Gardner Colour Difference Meter.

The poly(ethylene terephthalate) to polymers shown in -Examples 1--13 of Table I were prepared as follows: Example I (Comparative) (65) Zn - (230) Sb - (31) P Catalyst).

A ten mole ester interchange reaction was carried out by weighing 1942 g.

(10.0 moles) of dimethyl terephthalate (DMT) and 1390 g. (22.4 moles) of ethylene glycol into a 5000 ml reactor flask equipped with a mechanical stirrer, a thermometer well, and a packed distillation column such that methyl alcohol was permitted to distil from the reaction system, but the ethylene glycol was refluxed within the system. Weighed amounts of zinc acetate dihydrate (Zn(CH3CO2)2. 2H2O, M.W. 219) and antimony triacetate (Sb(CH3CO2)3, M.W.

299) were added to the reaction mixture so as to provide 65 ppm Zn and 230 ppm Sb based on the weight of the DMT fraction. Heat was applied (at about 155"C.) and the temperature of the reaction mixture was permitted to rise to about 225"C. as the reaction proceeded and methanol was distilled off. Heating was stopped when the theoretical amount of methanol (20.0 moles) had been recovered and the temperature of the reaction mixture had levelled off. Weighed amounts of the ester interchange reaction product were transferred to 500 ml reactor flasks, and the desired amount of the "Phosphate Ester A" described above was added to each portion of the reaction mixture. (The phosphate ester may be weighed in directly or may be added volumetrically, having first been dissolved in a suitable solvent such as ethylene glycol, n-butyl alcohol or methanol). The phosphate ester was added as a solution in n-butyl alcohol in an amount to provide 31 ppm P based on the weight of the DMT fraction of the ester interchange reaction product. (Other additives of interest such as stabilizers and delustrants may also be added at this time if desired).

The polycondensation reactor was then heated by immersing in a molten metal bath regulated at 275 + 2"C., the reactor system having first been flushed with dry nitrogen, and the reactor system was maintained under a dry nitrogen blanket until placed under vacuum.

The polycondensation reactor was equipped with a mechanical stirrer having suitable seals and with a system for condensing and collecting the excess ethylene glycol removed during the polycondensation reaction, and with suitable connections to permit evacuation of the reactor system during the polycondensation reaction. The polycondensation reactions were run at 275 1 2"C., and < 0.3 mm Hg absolute pressure for times sufficient to permit the inherent viscosity (I.V.) of the polyester to reach a level of 0.58 or higher (usually 1--2 hours, although this time varies depending upon the activity of the catalyst).

Example 2 (Comparative) (48) Ti - (62) P (Ti as titanium tetraisopropoxide).

Polymers were prepared by the procedures described in Example 1 except that a titanium catalyst was used, and the phosphate ester was added at the start of the ester interchange reaction instead of at its end. Titanium was added as a solution of titanium tetraisopropoxide [Ti(OCH(CH3)2)4 M.W. 284] in n-butyl alcohol in an amount 48 ppm Ti based on the weight of the DMT fraction of the ester interchange reaction mixture. The phosphate ester was added as a solution in nbutyl alcohol in an amount to provide 62 ppm P based on the weight of the DMT fraction of the ester interchange reaction mixture.

Example 3 (Comparative) (12) Mg - (48) Ti - (62) P Catalyst.

Polymers were prepared by the procedure of Example 2, except that the catalyst was a magnesium-titanium-n-butoxide Meerwein complex, prepared as described in United States Patent Specification No. 2,720,502, and added as a solution in n-butyl alcohol in an amount to provide 48 ppm Ti based on the weight of the DMT fraction of the ester interchange reaction mixture.

Example 4 (Comparative) (48) Ti - (62) P (Ti as acetyl triisopropyl titanate).

Polymers were prepared by the procedure of Example 2, except that the titanium catalyst was a solution of acetyl triisopropyl titanate (ATIP) in n-butyl alcohol in an amount to provide 48 ppm Ti based on the weight of the DMT fraction of the ester interchange reaction mixture. Acetyl triisopropyl titanate (M.W. 284) was prepared by adding slowly with stirring and cooling and under a dry atmosphere glacial acetic acid (CH3COOH, M.W. 60) to titanium tetraisopropoxide in an amount to provide a 1/1 molar ratio of acetic acid/titanium tetraisopropoxide. The isobutyl alcohol thus displaced by the acetic acid was not removed. This catalyst may be added to the ester interchange reaction mixture undiluted or as a solution in any of a number of suitable solvents such as n-butyl alcohol, methyl alcohol or ethylene glycol.

The phosphate ester A was added as a solution in n-butyl alcohol in an amount to provide 62 ppm P based on the weight of the DMT fraction of the ester interchange reaction mixture.

The results listed in Table 1 for the catalyst systems of Examples 1 to 4 are averages of three polycondensation reactions carried out on each product of the four ester interchange reactions.

Example 5 (Comparative) (232) Mn - (374) Sb - (44) P Catalyst.

A poly(ethylene terephthalate) polymer was prepared by a continuous melt phase process on production scale polyester manufacturing equipment. Manganese benzoate tetrahydrate (Mn(02CC"H5)2. 4H20, M. W. 369) and antimony triacetate were metered continuously with ethylene glycol as solutions, separately or combined in one solution, into dimethyl terephthalate (DMT) at such a rate as to provide 236 ppm Mn and 374 ppm Mn based on the weight of product polyester.

DMT and ethylene glycol were present in substantially the same proportions as in Example 1. Phosphate Ester A was likewise metered continuously to the production unit at a point after the ester interchange reaction section ot the unit as a solution in a suitable solvent and at a rate such as to provide 44 ppm P based on the weight of product polyester.

Example 6 (Comparative) (50) Mn - (48) Ti - (50) P (Ti as acetyl triisopropyl titanate).

Polymers were prepared as described in Example 1, except that a Mn-Ti-P catalyst system was used. Manganese benzoate tetrahydrate was added as a solution in ethylene glycol to the ester interchange reaction mixture in an amount to provide 50 ppm Mn based orf the weight of the DMT fraction. Acetyl triisopropyl titanate (ATIP) was added as a solution in n-butyl alcohol in an amount to provide 48 ppm Ti based on the DMT fraction of the ester interchange reaction mixture. Phosphate Ester A was added as a solution in ethylene glycol to the product of the ester interchange reaction in an amount to provide 50 ppm P based on the weight of the DMT fraction of the reaction product and prior to the polycondensation of the product.

The polycondensation reactions were carried out as described in Example 1.

The results in Table 1 are averages of three such polycondensation reactions.

Examples 7 and 8 (Comparative) (50) Mn - (60) Ti - (20) Co - (80) P (Ti as ATIP) (70) Mn - (60) Ti -- (20) Co -- (80) P These polymers were prepared by performing the ester interchange reaction and the polycondensation reaction consecutively in the 500 ml reaction flasks. described in Example 1. Thus 116.4 g. (0.6 mole) of DMT and 93.0 g. (1.5 moles) of ethylene glycol were placed in the reaction flask. To this mixture was added titanium as ATIP, manganese benzoate tetrahydrate, cobalt acetate trihydrate [Co(OOCCH3)2.3H2O, M.W. 231], all in separate ethylene glycol solutions or alternatively in one combined ethylene glycol solution, in the amounts necessary to provide the indicated levels of catalyst metals based on the weight of the DMT fraction of the ester interchange reaction mixture. Additionally, Phosphate Ester A was added as a solution in ethylene glycol in an amount to provide the indicated 80 ppm P based on the weight of the DMT fraction of the ester exchange reaction mixture.

The reactor flask was subsequently immersed in a molten metal bath regulated at 195 i 2"C. with a dry nitrogen atmosphere maintained in the reactor flask, and the ester interchange reaction was carried out for the time required to recover the theoretical amount of methyl alcohol (1.2 moles). the temperature of the metal bath was then raised to 275 i 2"C. the reactor system placed under vacuum, and the polycondensation reaction carried out as described in Example 1.

Example 9 (Comparative) (76) Mn - (48) Ti - (13) Co - (17) Li - (74) P Poly(ethylene terephthalate) polymers were prepared by a continuous melt phase process on production scale polyester manufacturing equipment. Manganese benzoate tetrahydrate in an ethylene glycol solution, acetyl triisopropyl titanate in an ethylene glycol solution, cobalt acetate trihydrate in an ethylene glycol solution, and lithium acetate dihydrate in an ethylene glycol solution were metered continuously as solutions, separately or combined in one solution, to the polyester production equipment containing dimethyl terephthalate at such a rate as to provide 76 ppm Mn; 48 ppm Ti; 13 ppm Co; and 17 ppm Li based on the weight of product polyester. The ethylene glycol and the DMT were present in substantially the same proportions as in Example 1. The Phosphate Ester A was metered continuously to the production unit at a point after the ester interchange reaction section of the unit as an ethylene glycol solution such as to provide 74 ppm P based on the weight of product polyester.

Example 10 (Comparative) (63) Mn - (58) Ti - (13) Co - (28) Li - (98) P.

The procedure of Example 9 was repeated, changing only the amounts of catalyst stabilizer components as indicated.

Example 11 (Comparative) (40) Mn - (21) Ti - (10) Co - (16) Li - (75) P A A polymer was prepared by a continuous melt phase process on polyester manufacturing equipment. Manganese benzoate tetrahydrate in an ethylene glycol solution, acetyl triisopropyl titanate in an ethylene glycol solution, cobalt acetate trihydrate in an ethylene glycol solution, and lithium acetate dihydrate in an ethylene glycol solution were metered continuously as solutions, separately or combined in one solution, to the polyester production equipment at such a rate as to provide 40 ppm Mn; 21 ppm Ti; 10 ppm Co; and 16 ppm Li based on the weight of product polyester. Phosphate Ester A was metered continuously to the production unit at a point after the ester interchange reaction section of the unit as an ethylene glycol solution such as to provide 75 ppm P based on the weight of product polyester.

Example 12 (Comparative) (44) Mn - (25) Ti - (15) Co- (19) Li and (97) P The procedure of Example 11 was repeated, changing only the amounts of catalyst stabilizer components as indicated.

Example 13 (29) Mn - (44) Ti - (13) Co - (72) Sb - (75) P The polymer was prepared by a continuous melt phase process on polyester manufacturing equipment. Manganese benzoate tetrahydrate in an ethylene glycol solution, acetyl triisopropyl titanate in an ethylene glycol solution, cobalt acetate trihydrate in an ethylene glycol solution, and antimony triacetate in an ethylene glycol solution were metered continuously as solutions, separately or combined in one solution, to the polyester manufacturing equipment at such a rate as to provide 29 ppm Mn. 44 ppm Ti, 13 ppm Co, and 72 ppm Sb based on the weight of product polyester. Phosphate Ester A was metered continuously to the manufacturing equipment at a point after the ester interchange reaction section of the unit as an ethylene glycol solution such as to provide 75 ppm P based on the weight of product polyester.

TABLE 2 Thermo-oxidative Stability of PET Made with Various Catalysts Thermo-oxidative Example Catalyst Composition (ppm) Stability 14 (100)Ca-(12) Co-(286)Sb-(190)P 1.000* 15 (99)Zn-(217)Sb-(281)P 2.89** 16 (53)Mn-(353)Sb-(170)P 1.876 17 (76)Mn-(132)Sb-(25)P 1.323 18 (1 19)Mn-( 10)Co-(292)Sb-(170)P 1.278 19 (113)Mn-(35)Co-(269)Sb-(130)P 1.043 20 (15)Mg-(60)Ti-(120)P 3.103 21 (50)Mn-(60)Ti-(20) Co-(80)P3 0.930 22 (72)Mn-(48)Ti-(16)Co-(20)Li-(118)P 0.530 23 (62)Mn-(36)Ti-(14)Co-(18)Li-(108)P 0.590 24 (40)Mn-(21)Ti-(10)Co-(16)Li-(75)P 0.634 25 (44)Mn-(25)Ti-(15)Co-(19)Li-(97)P 0.630 26 (29)Mn-(44)Ti-(13) Co-(7 2)Sb-(75)P3 0.971 * Standard to which all other results are normalized.

** Normalized percent crosslinker (thermo-oxidation product). Percent crosslinker correlates with percent weight loss (see 2). ppm metal based on wt. of polymer.

2 Percent weight loss of pressed films after 6 hours at 3000C. in air circulating oven. All results are normalized by dividing percent weight loss by the percent weight lost by the standard 3 Ti as acetyl triisopropyl titanate.

The poly(ethylene terephthalate) polymers set forth in Examples 1426 in Table 2 were prepared as follows: Example 14 (Comparative) (100) Ca - (12) Co - (286) Sb - (190) P.

This polymer was a commercially available product manufactured by Teijin Ltd. having an inherent viscosity of 0.62, and which had been made using this four compone phosphate ester was added by blending 50.0 g. of the polymer pellets with the required amount of phosphate ester in 25 ml. of dry benzene to provide 281 ppm of P based on the weight of polyester. The benzene was then evaporated off under vacuum, and the coated pellets dried and then extruded on a Brabender Plasticorder melt extruder to obtain homogeneous mixing of the phosphate ester.

Example 16 (Comparative) (53) Mn - (353) Sb - (170) P (Mn as manganese benzoate, Sb as antimony triacetate and P as phosphate ester A).

This polymer was prepared using the procedure described in Example 1.

Example 17 (Comparative) (76) Mn - (132) Sb - (25) P.

This polymer was produced as described in Example 5.

Examples 18 and 19 (Comparative) (119)Mn-(10)Co-(292)Sb-(170)P (113)Mn-(35)Co-(269)Sb-(130)P (Mn as manganese benzoate, Co as cobalt acetate. Sb as antimony triacetate and P as phosphate ester A).

These polymers were prepared as described in Example 7, except that the phosphate ester was coated on the polymer as follows: the polymer was ground through a 2 mm screen and then 20 g. was blended with a sufficient amount of Phosphate Ester A in 50 ml of dichloromethane (Ch2Cl2, M...W. 85) to give the indicated levels of P (ppm based on the weight of polyester). The dichloromethane was then evaporated off under vacuum.

Example 20 (Comparative) (15) Mg - (60) Ti - (120) P (Mg and Ti as a magnesium-titanium complex, as described in Example 3, and P as phosphate ester A).

This polymer was produced by the continuous melt phase process described in Example 5.

Example 21 (Comparative) (50) Mn - (60) Ti - (20) Co - (80) P.

This polymer was prepared as described in Example 7.

Examples 22 and 23 (Comparative) (72)Mn-(48)Ti-(16)Co-(20)Li-(118)P (62)Mn-(36)Ti-(14)Co-(18)Li-(108)P These polymers were prepared by the procedure described in Example 9.

Examples 24 and 25 (Comparative) (40)Mn-(21)Ti-(10)Co-(16)Li-(75)P (44)Mn-(25)Ti-(15)Co-(19)Li-(97)P These polymers were prepared by the procedure set forth in Example 11.

Example 26.

(29) Mn - (44) Ti - (13) Co - (72) Sb - (75) P The polymer was prepared using the procedure described in Example 13.

TABLE 3 Effect of Catalyst Composition on Colour Shift of Dyed Yarn Heat Set Colour Shift, Catalyst Composition (ppml) I,V.2 A K/S (80)Mn-(56)Ti-(22)Co-(99)P 0.61 b (80)Mn-(48)Ti-(15)Co-(84)P 0.56 b (90)Mn-(56)Ti-(18)Co-(23)Li-(134)P 0.53 a (56)Mn-(65)Ti-(18)Co-(13)Li-(73)P 0.57 0.0130, c (40)Mn- (22) Ti-(15)Co-(67)P 0.54 0.0254, b (51)Mn-(57)Ti-(19)Co-(100)Na-(64)P 0.63 0.0014, c (236) Mn-(37 4) St-(44) P 0.65 a (40)Mn-(2 1)Ti-(10)Co-( 16)Li-(7 5)P 0.63 a (44)Mn-(25)Ti-(15)Co-(19)Li-(97)P 0.63 a (8 4)Mn-(7 3) Sb-(69)Ti-( 19)Co-(123) P 0.608 a (47)Mn-(1 12)Sb-(28)Ti-( 18)Co-(112)P 0.49 0.0039 (a) (44)Mn-(143)Sb-(50)Ti-(18)Co-(58)P 0.62 a (50)Mn-(94) Sb-(52)Ti-(l0)Co-(67)P 0.59 a ppm metal based on polyester polymer 2 Inherent viscosity of 0.5 g/100 ml of 60/40 (w/w) phenol/tetrachloroethane at 250C. a Colour shift after heat set treatment equal to or better than the control by visual comparison. b Colour shift compared to the control is too great for acceptance by visual comparison. c Acceptable.

The data set forth in Table 3 particularly illustrate the effects of anitmony, when used with Mn-Co-Ti-P compositions, on the bathochromic colour shift of dyed yarn. The polymers were made in the manner shown in Examples 7 and 8 for the Mn-Co-Ti-P composition and in Examples 9 and 18 for the Mn-Ti-Co-Sb-P composition. The polymer for which the Mn-Ti-Co-Na-P composition was used was made in the manner described in Examples 7 and 8, the sodium being added as sodium acetate (anhydrous) in an ethylene glycol solution.

The K/S value used is determined by use of colour measurement with a spectrophotometer. The spectrophotometer can be used to measure the percent diffuse reflectance of a sample for a given wavelength from 800 to 380 nm. The K/S term is the ratio of the absorptivity coefficient (K) to the scattering coefficient (S) and is related to the diffuse reflectance (R) as follows: (I-R)2 (I~ R)2 2R Further K/S = k loggO Conc., but if the dyeing level for all samples is maintained constant (in the table above the dyeing level was 0.3% by weight) then an observed colour shift in a dyed sample manifests itself as a change in the constant k. l he term QK/S was chosen to represent the change in K/S which occurred upon heat setting of certain dyed polyester samples as set forth above. Diffuse reflectance was measured at 620 nm for each sample before and after heatsetting. The respective K/S values were calculated, and the difference, K/S heatset minus K/S nonheatset, is reported as AK/S. The equipment used was a Spectrosystem 100 Spectrophotometer sold by Cary Instruments of Monrovia, California.

Example 27.

Set forth in the table below are data showing the effect of the catalyst composition of this invention in improving the solid state polycondensation rate of poly(ethylene terephthalate) in comparison with other catalyst compositions. The data in the table below were obtained by the following procedure.

A small sample of polymer pellets (as produced) was crystallized by heating for 30 minutes in an oven at 1800 C. under a nitrogen blanket. A 2 gram sample of the crystalline pellets was then placed in a test tube which was then evacuated to an absolute pressure of < 0.2mm. Hg. The test tube was placed in an aluminium heat block regulated at 240"C, After 18 hours in the heat block, the test tube was removed and allowed to cool to room temperature while remaining under vacuum.

The vacuum was relieved and the sample removed for inherent viscosity (I.V.) determination. The final I.V. was compared with the starting I.V. as a measure of solid state activity. The average polycondensation rate over the test period may than be expressed as change in I.V. per hour.

Final I.V.-Initial I.V.

#I.V./Hr. = Time (Hrs.) Note the increased activity of the polymer produced using the catalyst compositions of this invention (item 6).

TABLE Initial Final Item No. Catalyst Composition* I.V. I.V. AI.V. /Hr.

1 (82)Mn(24)Co-(82)Ti-(100)P 0.62 1.06 0.024 2 (92)Mn-(24) Co-(80)Ti-(102) P 0.60 1.03 0.024 3 (65)Mn-(10)Co-(34)Ti-(23)Li-(106)P 0.58 0.9'** 0.019 4 (60)Mn-g)Co-(56)Ti-(21)Li-(76)P 0.58 0.98** 0.022 5 (64)Mn-(34)Ti-(78)P 0.64 1.04 0.022 6 (32)Mn-(72)Co-(28)Ti-(244)Sb(122)P 0.61 1.14 0.029 * Parts per million of metal based on polymer weight.

** Average of two runs.

Claims (23)

WHAT WE CLAIM IS:

1. A process for producing poly(ethylene terephthalate) wherein dimethyl terephthalate and ethylene glycol are reacted at a temperature sufficient to effect ester interchange and in the presence of a catalytic amount of a catalyst comprising a mixture of organic or inorganic salts of manganese and cobalt with a titanium alkoxide and antimony or an antimony compound, and the ester reaction product of the ester interchange is polycondensed.

2. A process as claimed in Claim 1, wherein the manganese salt is present in the amount of 25-110 ppm Mn, the cobalt salt is present in the amount of 10100 ppm Co, the titanium alkoxide is present in the amount of 2060 ppm Ti, and the antimony or antimony compound is present in the amount of 50-300 ppm antimony, all parts being parts by weight based on the acid fraction of the polyester.

3. A process as claimed in Claim I or 2, wherein the manganese salt is selected from manganous benzoate tetrahydrate, manganese chloride, manganese oxide, manganese acetate, manganese acetylacetonate, manganese succinate, manganese diethyldithio-carbamate, manganese antimonate, manganic phosphate monohydrate, manganese glycoxide, manganese naphthenate and manganese salicyl salicylate.

4. A process as claimed in Claim 1, 2 or 3, wherein the cobalt salt is selected from cobaltous acetate tetrahydrate, cobaltous nitrate, cobaltous chloride, cobalt acetylacetonate, cobalt naphthenate and cobalt salicyl salicylate.

5. A process as claimed in any one of Claims 1 to 4, wherein the titanium alkoxide is selected from acetyl triisopropyl titanate, titanium tetraisopropoxide, titanium glycolates, titanium butoxide, hexylene glycol titanate and tetraisooctyl titanate.

6. A process as claimed in any one of Claims I to 5, wherein the antimony or antimony compound is selected from antimony metal or metal alloys, antimony III and V halides, hydroxides and sulphides; antimony III, IV and V oxides; antimony salts of carboxylic acids; antimony III and V glycolates: antomony alcoholates such as

where RX, R2, and R3 are alkyl or cycloalkyl radicals which may include inert substituents: alkyl antimonites; metal antimonates and divalent metal antimonites.

7. A process as claimed in Claim 1 or 2, wherein the manganese salt is manganous benzoate tetrahydrate and the cobalt salt is cobaltous acetate tetrahydrate, the titanium alkoxide is acetyl triisopropyl titan ate and the antimony compound is antimony triacetate.

8. A process as claimed in any one of Claims 1 to 7, wherein a phosphate ester is added to the ester reaction product of the ester interchange and the reaction product is polycondensed, the phosphate ester being present in the amount of 13 to 240 ppm of phosphorus based on the acid fraction of the polyester.

9. A process as claimed in Claim 8, wherein the phosphate ester is selected from ethyl dihydrogen phosphate, diethyl hydrogen phosphate, triethyl phosphate, aryl alkyl phosphates, tris-2-ethylhexyl phosphate and a phosphate ester having the formula

wherein n has an average value of 1.5 to 3.0 and each R is hydrogen or an alkyl radical having from 6 to 10 carbon atoms, the ratio of the number of acidic hydrogen atoms represented by R to the number of phosphorus atoms being 0.25 to 0.50, and the ester has a free acidity equivalent of 0.2 to 0.5.

10. A process as claimed in Claim 9, wherein n is 1.8, R is hydrogen or octyl and the ratio of the number of acidic hydrogen atoms represented by R to the number of phosphorus atoms is 0.35.

11. A process as claimed in Claim 9, wherein the phosphate ester has a molecular weight of 771 and the composition is as follow: C = 52.84%: H = 9.98%, P = 8.04%; and 0 = 29.14% by weight.

12. A process as claimed in Claim 1 and substantially as hereinbefore described.

13. Poly(ethylene terephthalate) made by a process as claimed in Claim 1.

14. Poly(ethylene terephthalate) made by a process as claimed in any one of Claims 2 to 11.

15. A catalyst composition comprising a mixture of organic or inorganic salts of manganese and cobalt with a titanium alkoxide and antimony or an antimony compound.

16. A catalyst composition as claimed in Claim 15 and being suitable for catalyzing an ester interchange reaction between dimethyl terephthalate and ethylene glycol, the ester reaction product being polycondensable to prepare a polyester, wherein the manganese salt is present in the amount of 25-110 ppm Mn, the cobalt salt is present in the amount of 10--10qppm Co, the titanium alkoxide is present in the amount of 20-60 ppm Ti, and the antimony or antimony compound is present in the amount of 50-300 ppm antimony, all parts being parts by weight based on the acid fraction of the polyester which is to be prepared.

17. A catalyst composition as claimed in Claim 15 or 16, also comprising a phosphate ester present in the amount of 13-240 ppm P by weight based on the acid fraction of the polyester which is to be prepared.

18. A catalyst composition as claimed in Claim 15, 16 or 17, wherein the manganese salt is selected from manganous benzoate tetrahydrate, manganese chloride, manganese oxide, manganese acetate, manganese acetylacetonate, manganese succinate, manganese diethyldithiocarbamate, manganese antimonate, manganic phosphate monohydrate, manganese glycoxide, manganese naphthenate and manganese salicyl salicylate.

19. A catalyst composition as claimed in any one of Claims 15 to 18, wherein the cobalt salt is selected from cobaltous acetate tetrahydrate, cobaltous nitrate, cobaltous chloride, cobalt acetylacetonate, cobalt naphthenate and cobalt salicyl salicylate.

20. A catalyst composition as claimed in any one of Claims 15 to 19, wherein the titanium alkoxide is selected from acetyl triisopropyl titanate, titanium tetraisopropoxide, titanium glycolates, titanium butoxide, hexylene glycol titanate, and tetraisooctyl titan ate.

21. A catalyst composition as claimed in any one of Claims 15 to 20, wherein the antimony or antimony compound is selected from antimony metal or metal alloys; antimony III and V halides, hydroxides and sulphides; antimony salts of carboxylic acids; antimony III and V glycolates; antimony alcoholates such as

where R1, R2 and R3 are alkyl or cycloalkyl radicals which may include inert substituents; alkyl antimonites; metal antimonates; and divalent metal antimonites.

22. A catalyst composition as claimed in any one of claims 17 to 21, wherein the phosphate ester is selected from ethyl dihydrogen phosphate, diethyl hydrogen phosphate, triethyl phosphate, aryl alkyl phosphates, tris-2-ethylhexyl phosphate and a phosphate ester havingthe formula

wherein n has an average value of 1.5 to 3.0 and each R is hydrogen or an alkyl radical having from 6 to 10 carbon atoms, the ratio of the number of acidic hydrogen atoms represented by R to the number of phosphorus atoms being 0.25 to 0.50, and'the ester has a free acidity equivalent of 0.2 to 0.5.

23. A catalyst composition as claimed in Claim 15, and substantially as hereinbefore described.