United States Patent to 11, 4,020,010 Vogt et al. 45 Apr. 26, 1977 54) TIN TITANIUM COMPLEXES As (56) References Cited ESTERIFICATION/TRANSESTERIFICA. TON CATALYSTS UNITED STATES PATENTS 3,056,818 10/1962 Werber ...... 252/431 C (75) Inventors: Herwart C. Vogt, Grosse Ile; Manher 3,714,234 i? 1973 White ...... 252/431 R 3,716,523 2/1973 Cook ...... 260/75 M Parekh, Woodhaven; John T. Patton, Jr., Wyandotte, all of Mich. 3,884,832 5/1975 Pullukat ...... 252/43 R Primary Examiner-Winston A. Douglas (73) Assignee: BASF Wyandotte Corporation, Assistant Examiner-John F. Niebling Wyandotte, Mich. Attorney, Agent, or Firm-Norbert M. Lisicki; Bernhard R. Swick; Robert E. Dunn 22) Filed: Dec. 29, 1975 57 ABSTRACT (21) Appl. No.: 644,357 Complexes of stannous carboxylate and tetraalkyl tita nate are effective esterification and transesterification (52) U.S. C...... 252/431 C; 252/431 R catalysts. (51) int. C.’...... B01J 31/2 (58) Field of Search ...... 252/431 R, 431 C 7 Claims, No Drawings 4,020,010 1. 2 tetraaryl titanate will result in complexes which are TIN TITANIUM COMPLEXES AS more efficient than the individual metal components as ESTERIFICATION/TRANSESTERIFICATION esterification/transesterification catalysts. The com CATALYSTS plexes may be used for any type of mono- or polycar boxylic acid and anhydride to be esterified with any BACKGROUND OF THE INVENTION suitable hydroxyl containing material. 1. Field of the Invention This invention relates to the preparation of tin DESCRIPTION OF THE PREFERRED titanium complexes. More specifically, this invention EMBODIMENTS relates to a process of preparing esters and polyesters in 10 The tin-titanium complex may be described by the an improved manner by using these novel complexes as following general formula: esterification/transesterification catalysts. 2. Prior Art The preparation of esters and polyesters is well known in the art. These materials are prepared by es 15 terifying mono- and/or polyhydric alcohols with mono Ti(OR), Sn OCR' U , and/or polycarboxylic acids. In many instances it is desirable to prepare such esters or polyesters having a very low acid number, i.e., less than two. However, the wherein R is a radical selected from the group consist attainment of an ester or polyester having a low acid 20 ing of an aliphatic radical having from 1 to 18 carbon number is extremely difficult to achieve. For example, atoms, an alicyclic radical having between l and 3 during the last stage of the esterification of the reac rings, between 5 and 6 carbon atoms per ring and be tion, the reaction proceeds extremely slowly and hence tween 5 and 18 carbon atoms per molecule, and an in order to reduce the acid value it is necessary to heat aromatic radical having between l and 3 rings and for a lengthy period of time at relatively high tempera 25 between 6 and 18 carbon atoms per molecule, R' is an tures. This, in many instances, tends to bring about organic radical having from 1 to 18 carbon atoms and formation of a darkened ester or polyester which is x and y are whole numbers in the ratio of 1:1 to 1:8. unsuitable for further use. Various attempts have been The complexes of this invention are prepared by made to reduce the time of the esterification reaction. reacting together, under anhydrous conditions, and in For instance, British Pat. No. 792,011 describes the use 30 the absence of air, at room temperature, the desired of iron, cadmium, cobalt, lead, zinc, antimony and concentration of stannous carboxylates with the de manganese in the form of the metal, its oxide or its salt sired amount of tetraalkyl or tetraaryl titanate. It may with a bibasic acid. Other catalyst types are more reac also be desired to heat the reactants if shorter reaction tive. For example, stannous compounds of the type times are desired and to assure completeness of reac Sn(OOCR), wherein R is selected from the group con 35 tion. The reaction of these two clear liquids is often sisting of saturated and unsaturated aliphatic hydrocar accompanied by orange, light yellow, or red color for bon constituents having from about 7 to about 17 car mation and the liberation of heat. Sometimes it is desir bon atoms have been described in U.S. Pat. No. able to carry out this preparation in a suitable inert 3,162,616 and U.S. Pat. No. 3,716,523. Organo tita solvent to permit easier handling of the complex. Sol nium or organo zirconium compounds have been dis 40 vents such as anhydrous xylene may be employed. In closed by U.S. Pat. No. 3,056,818 as being suitable as addition to the color formation and heat evolution esterification catalysts. Titanium compounds are often which indicate a new complex compound has been insoluble in the product and must be removed by filtra formed, it has been found that the tin-titanium complex tion or other tedious procedures. The technical litera has improved hydrolytic stability. It is well known that ture also notes that esterification is usually effected by 45 stannous salts of organic acids and titanium alkylates refluxing the acid and with a small amount of are very susceptible to trace amounts of moisture acid catalyst such as sulfuric acid, hydrochloric acid, which leads to rapid hydrolysis, catalyst deactivation, and sulfonic acids or boron trifluoride. Acid catalyst and often solid formation. For example, tetrabutyl tita often causes color formation and must be removed to nate is immediately decomposed by water forming insure a stable low acid number product. 50 titanic acid. Atmospheric moisture may produce high Esters may also be prepared by transesterification molecular weight condensation products which pro reactions. These transesterification reactions include ceed until titanium dioxide or the hydrous titanium the reactions between two esters to yield two new es dioxide is formed. Stannous octoate undergoes similar ters or the reaction between an ester and an alcohol to hydrolysis type reactions with water and precautions form a new ester and liberate an alcohol. Included also 55 must be taken to prevent the destruction of the cata are the transesterification reactions where the compo lyst. nents of the esters involved are polyhydroxy alcohols Any suitable stannous salt of a carboxylic acid may and polybasic acids. These reactions may, in some be used to prepare the complex. These may be de instances, be catalyzed by those substances which are scribed by the following formula: employed for the esterification procedure. We have 60 discovered that polyesters having an acid number less Sn(OOCR) than two can be prepared in relatively short period of time with tin-titanium catalyst complexes employing wherein R is a saturated or unsaturated, straight or either esterification or transesterification procedures. branched chain, aliphatic or aromatic substituent hav 65 ing from about 1 to about 18 carbon atoms in its chain. SUMMARY OF THE INVENTION Stannous octoate and stannous oleate are preferred. It has been discovered that certain unique combina Other suitable stannous salts are stannous naphthenate, tions between a tin carboxylate and a tetraalkyl or stannous acetate, stannous butyrate, stannous ethyl 4,020,010 3 4 hexoate, stannous laurate, stannous palmitate, and removal at the later stages of esterification, a vacuum StanOuS Stearate. of 0.1-100 mm Hg is employed. The time of reaction The titanium compounds which are employed can be will depend on the reactivity of the reactants, the stoi represented by the general formula: chiometry, temperature, and pressure employed in the 5 reaction, the molecular weight of the resulting polyes Ti(OR) ter, the rapidity with which the water of esterification is removed, and the activity of the catalyst employed, if wherein R is a radical selected from the group consist any. ing of an aliphatic radical having from 1 to 18 carbon Any mono- or polycarboxylic acid and anhydrides atoms, an alicyclic radical having between l and 3 () thereof may be employed for the preparation of esters. rings, between 5 and 6 carbon atoms per ring, and Thus, the acids undergoing esterification can be ali between 5 and 18 carbon atoms per molecule, and an phatic, cycloaliphatic or aromatic and they can be aromatic radical having between l and 3 rings and substituted or unsubstituted. Among the acids which between 6 and 8 carbon atoms, per molecule. may be employed include acetic, acrylic, propionic, Examples of these compounds include tetramethyl propiolic, isobutyric, methacrylic, n-butyric, pivalic, titanate, tetraethyl titanate, tetraally titanate, tetrapro ethylmethylacetic, isovaleric, chloroacetic, o-chloro pyl titanate, tetraisopropyl titanate, tetrabutyl titanate, propionic, n-valeric, dichloroacetic, diethylacetic, tetraisobutyl titanate, tetraamyl titanate, tetracyclo isocaproic, o-ethyl-n-butyric, methoxyacetic, n pentyl titanate, tetrahexyl titanate, tetracyclohexyl caproic, ethoxyacetic, bromoacetic, heptoic, o-ethyl-n- titanate, tetrabenzyl titanate, tetraoctyl titanate, tetrae () caproic, a-bromoisovaleric, hexahydrobenzoic, di thylhexyl titanate, tetranonyl titanate, tetradecyl tita bromoacetic, n-caprylic, a-phenylpropionic, un nate, and tetraoleyl titanate. decanoic, g-phenylpropionic, mesity lenic, tricarbally Mixed alkyl titanate compounds wouid include lic, o,6-dibromosuccinic, tartaric, 3,5-dinitrosalicyclic, trimethylbutyl titanate, dimethyldibutyl titanate, trie p-toluic, acetylenedicarboxylic, veratric (anhydrous), thylbutyl titanate, methyl isopropyl dibutyl titanate, 2 5 p-fluorobenzoic, 2,4-dinitrobenzoic, anisic, g-naph diethyl dibutyl titanate, propyl tributyl titanate, ethyl thoic, acetylanthranilic, camphoric, hippuric, succinic, tricyclohexyl titanate, diisopropyl dioctadecyl titanate, aconitic, m-nitrocinnamic, 2-chloro-3,5-dinitroben and dibutyl dioctadecyl titanate. zoic, fumaric, m-hydroxybenzoic, p-coumaric, Included among the aromatic titanates are tetraphe phthalic, o-coumaric, p-hydroxybenzoic, g-resorcylic, nyl titanate, o- and m-tetramethylphenyl titanate, and tetrachlorophthalic, p-bromobenzoic, isophthalic, ter 1- and 2-tetranaphthyl titanate. ephthalic, trimesic, 6-benzoylpropionic, p-isopropyl The concentrations of complex which may be em benzoic, benzoic, o-benzoylbenzoic, y-benzoylbutyric, ployed in the preparation of ester or polyester polyols 2,4-dimethylbenzoic, maleic, o-(p-toluyl)-benzoic, 2.5- can be varied over a fairly wide range. Small amounts dimethylbenzoic, sebacic, mandelic, cinnamic, acetyl such as 0.00002 mole of complex (0.2 x 10') per : salicylic, phenylpropiolic, glutaconic (cis), glutaconic 1000 grams of ester or polyester have been successfully (trans), 2,6-dichlorobenzoic, o-chlorobenzoic, m employed and amounts as high as 0.0174 mole of com nitrobenzoic, meso-tartaric, suberic, furylacrylic, o plex (174 x 10') per 1000 grams of polymer or higher nitrophenylacetic, 3-nitrosalicyclic, diphenylacetic, can be used. Preferably, amounts less than 0.00174 o-nitrobenzoic, phthalonic, p-hydroxyphenylacetic, mole of complex (17.4 x 10") per 1000 grams of ester o-bromobenzoic, benzilic, adipic, p-nitrophenylacetic, or polyester are employed. The presence of large quan 2,5-dichlorobenzoic, citric, m-bromobenzoic, 2,4,6- tities may result in the presence of an unwanted impu trimethylbenzoic, salicyclic, m-chlorobenzoic, 2,4- rity depending upon the future use of the ester or poly dichlorobenzoic, a-naphthoic, 2,3-dichlorobenzoic, ester polyol. Although the complex may be initially 3,4-dimethylbenzoic, oleic, methacrylic, latic, g introduced with the material to be esterified, it is pre bromoisobutyric, thiobenzoic, undecylenic, un ferred to introduce the complex at the time when the decanoic, hexahydrobenzoic, capric, pivalic, 6-chloro esterification reaction has slowed down and the acid propionic, lauric, angelic, dibromoacetic, g-phenylpro number has reached a value of about 15-20. Reaction pionic (hydrocinnamic),a-bromoisobutyric, bromoa conditions under which esterification is effected can be cetic, elaidic, y-phenylbutyric, myristic, trichloroace varied considerably. The reaction generally proceeds tic, 6-bromopropionic, palmitic, chloroacetic, ag very slowly at room temperature but at elevated tem dibromopropionic, cyanoacetic, stearic, crotonic peratures, preferably under reflux, the reaction rate is (trans), phenylacetic, glycolic, citraconic, phenoxyace quite rapid so that about 99 percent of the acid is con tic, phthalaldehydic, glutaric, o-methoxybenzoic, o verted to ester within a few hours. To force the equilib toluic, pimelic, azelaic, m-toluic, ethylmalonic, ma rium towards the formation of the product the water of 55 lonic, suberic, brassylic, thapsic, fumaric, glutaconic, esterification is removed as rapidly as it forms. One o-hydromuconic, g-hydromuconic, o-butyl-o-ethyl accepted way this can be accomplished is by carrying glutaric, o,6-diethyl succinic, isophthalic, terephthalic, out the reaction in a liquid medium which forms an hemimellitic, 1,4-cyclohexane dicarboxylic. azeotrope with water having a boiling point that is Anhydrides of mono- and polybasic acids can be used lower than that of either component of the reaction. It 6) in place of the acids. These include acetic anhydride, is to be understood however, that if the reactants and propionic anhydride, n-butyric anhydride, citraconic the esters which result, boil at temperatures well above anhydride, n-valeric anhydride, crotonic anhydride, 100° Centigrade at atmospheric pressure, the reaction n-heptoic anhydride, benzoic anhydride, chloroacetic temperature can be sufficiently high and would not anhydride, maleic anhydride, itaconic anhydride, 4 require azeotrope forming liquid reaction medium. 65 nitrophthalic anhydride, succinic anhydride, cinnamic Generally, temperatures of 150-250 Centrigrade are anhydride, phthalic anhydride, 1,2-naphthalic anhy employed. The reaction can be carried out under re dride, camphoric anhydride, 2,3-naphthalic anhydride, duced or superimposed pressures. To facilitate water o-naphthoic anhydride, 1,8-naphthalic anhydride, tet 4,020,010 S 6 rabromophthalic anhydride, and tetrachlorophthalic oleate at 23° Centigrade. The temperature rose to 36 anhydride. Centigrade and a dark red color developed. Among the monohydric and polyhydric alcohols which can be reacted with carboxylic acids and anhy EXAMPLES 3-19 drides include methyl alcohol, ethyl alcohol, isopropyl The following series of experiments in Table I below alcohol, tert-butyl alcohol, allyl alcohol, n-propyl alco were conducted to determine the hydrolytic stability of hol, sec-butyl alcohol, tert-amyl alcohol, isobutyl alco titanium/tin complexes. The mole ratio of stannous hol, methylisopropylcarbinol, n-butyl alcohol, diethyl carboxylate/tetraalkyl titanate was increased as shown carbinol, sec-amyl alcohol, mono below. The molar concentration of water was kept methyl ether, 1-chloro-2-propanol, sec-butylcarbinol, 10 constant. The indicated amounts of each component ethylene chlorohydrin, , 4-methyl-2- were added to glass test tubes, stoppered and vigor pentanol, 2-chloro-1-propanol, ethylene glycol mono ously shaken. The solutions were then observed for any ethyl ether, 3-hexanol, methylisobutylcarbinol, n-amyl development of haze indicating hydrolysis had oc alcohol, cyclopentanol, 2-ethyl-l-butanol, 2-bromoe curred. thanol, di-n-propylcarbinol, n-hexyl alcohol, 2-hep 15 tanol, 2-methylcyclohexanol, furfuryl alcohol, ethylene Table glycol mono-n-butyl ether, 4-methylcyclohexanol, 3 Ex- Mole Moles of Moles of Moles ample Ratio Com- Con- of Water methylcyclohexanol, , trichloroethyl alco pound pound hol, lauryl alcohol, cinnamyl alcohol, cy-terpineol, o N. A:C A X () C x 10' X 10.' Appearance tolycarbinol, myristyl alcohol, menthol, anisyl alcohol, 3 :1 5() 5() 55 Clear solution pinacol hydrate, p-tolycarbinol, , triphenylcar 4 2: 5() 25 55 Clear solution binol, , benzopinacol, borneol, , penta 5 4: 50 12.5 55 Clear solution 6 8: 50 6.25 55 Slightly hazy , diisobutylcarbinol, n-heptyl alcohol, tetrahy 7 16:1 5) 3.25 55 Slightly hazy drofurfury alcohol, 2-octanol, cyclohexycarbinol, 2,3- Ex- Mole Moles of Moles of Molcs dichloro-1-propanol, 2-ethyl-1-hexanol, propylene gly ample Ratio Com- Com- of Water col, n-octyl alcohol, diethylene glycol monomethyl pound pound ether, ethylene glycol, diethylene glycol monoethyl No. A:D. A x 10 D x 10' X 10. Appearance 8 : 50 5) 55 White preci. ether, methylphenylcarbinol, benzyl alcohol, n-nonyl pitate alcohol, trimethylene glycol, m-tolylcarbinol, 9 9 2: 50 25 55 Clear solution phenylethyl alcohol, ethylphenylcarbinol, diethylene 30 1() 4:l 50 12.5 55 Clear solution 11 8:75) 6.25 55 Slightly glycol mono-n-butyl ether, n-decyl alcohol, y-phenyl hazy propyl alcohol, diethylene glycol, ethylene glycol mon Ex- Mole Moles of Moles of Molcs ample Ratio Com- Com- (f Water ophenyl ether, cinnamyl alcohol, , benzohy pound pound drol, dipropylene glycol, triethylene glycol, tetraethyl N. B:C B x t () C x 10' x 10" Appearance ene glycol, 1,4-tetramethylene glycol, 1,2-butylene 35 12 : 50 50 55 White preci glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pen pitate tanediol, 1,4-pentanediol, 1,3-butanediol, 1,6-hex 13 2: 5() 25 55 Clear solution 14 4: 5) 2.5 55 Clear solution anediol, 1,7-heptanediol, glycerol, 1,1,1-trimethylol 15 8: 5) 6.25 55 Clear solution propane, 1,1,1-trimethylolethane, hexane-1,2,6-triol, Ex- Mole Moles of Mcles of Moles neopentyl glycol, 1,10-decanediol, and 2,2-bis (4- 40 ample Ratio Com- Con- of Water hydroxycyclohexyl) propane. pound pound The following Examples are provided to further illus No. B:D B X 10 D x 10' X 10 Appearance 16 :1 50 5() 55 White preci trate the invention. In these Examples the compounds pitate designated by letters A, B, C, D, and E are as follows: 7 2: 50 25 55 Clear solution Compound A is stannous octoate. 45 18 4:1 50 2.5 55 Clear solution Compound B is stannous oleate. 19 8: 50 6.25 55 Clear solution Compound C is tetrabutyl titanate. Compound D is tetraisopropyl titanate. Compound E is tetrakis-2-ethylhexyl titanate. EXAMPLES 20-29 The designations CIA, C/2A, D/2B, etc., indicate the 50 relative mole ratios of the respective compounds em The polyester of the following Examples was pre ployed to form the complexes. Parts and percents are pared by the following procedure: Into a 22-liter, four-neck, round bottom reaction by weight unless otherwise indicated. vessel, equipped with stirrer, thermometer, vacuum EXAMPLE I 55 pump, condenser, nitrogen gas sparge tube, and heater, In a 300-milliliter round bottom flask equipped with 1,4-butanediol (3225 g. = 35.8 moles), ethylene glycol a stirrer, thermometer, dropping funnel, and nitrogen (2226 g. = 35.8 moles) and adipic acid (9549 g. = 65.4 sparge, 17.02 grams (0.050 mole) tetrabutyl titanate moles) were added. The reaction mixture was gradually was carefully added with stirring to 40.40 grams (0.100 heated to 170°-180° Centigrade with the water of reac mole) stannous, octoate dissolved in 172.3 grams xy 60 tion being removed continually. When the rate of water lene (anhydrous), at 25 Centigrade. The temperature removal slowed down, the reaction temperature was of the mixture rose slightly and a yellow-orange color increased to 225 + 5° Centigrade and vacuum was developed. slowly and carefully applied until a vacuum of 10 mm Hg was reached. The reaction was stopped when the EXAMPLE 2 65 polyester mixture had an acid number of 18.73. This Using equipment similar to that described in Exam was stored and used as a master batch for investigation ple 1, 13.03 grams (0.0458 mole) tetraisopropyl tita of the catalytic effect of various compounds on the acid nate was added to 62.50 grams (0.0916 mole) stannous numbers of this polyester in Examples 20-29. 4,020,010 7 8 The polyester, l 160 grams, was transferred to a two liter, round bottom reaction flask, equipped with stir Table III-continued rer, thermometer, vacuum pump, condenser, nitrogen Examples gas sparge tube and heater. The polyester was then Components, gms. 3) 31 32 33 heated to 225. 5 Centigrade and a sample again acid number, hrs. 22 6 8 16 removed to determine the initial acid number. The designated compound was then added and the polyes ter mixture was allowed to react for one hour. The acid number was checked and additional compound added EXAMPLES 34-35 as indicated. The mixture was then reacted for an addi- 10 The procedure using the equipment of Examples tional hour and the final acid number was then deter 30-33 was followed in the subsequent Examples with mined. The results in Table II indicate that the com one difference. The flask was charged with the glycol plexes are considerably more reactive than the individ and the anhydride followed by an addition of 11.0 ual compounds as indicated by the concentration of grams of sodium acetate. This mixture was stirred for compound required to achieve the final acid number. 15 about one hour followed by the addition of the adipic The variations in the initial acid number are due to a acid. The remainder of the procedure of Example 30 variation in the time of heating the individual polyester was then followed. The addition of the sodium acetate mixture prior to addition of the various compounds. is intended to neutralize any residual acidity of the acid Table II Fxamples 20 2 22 23 24 25 26 27 28 29 Compound C CIA CF2A C13A CF4A A D B D/2B D/2A Initial Acid Number 1546 6.9 14.98 9.34 17.32 4.32 7.06 1542 7.60 7.95 Amount of Compound, st Addition, gns. ().()3 ()3 ().03 0.03 ().03 (), ()3 0.03 ().03 0.03 0.03 Aci. Number after hur 7 73 (),8 5.32 5.20 4.6) ().97 7.45 3.83 0.86 Amount of Compound, 2nd Addition, gms. (),03 ().()3 (), ()() ().()3 (),)3 0.03 ().)3 ().03 0.03 0.03 Aciul Nunhet after 2 hours ().29 (39 (),48 ().35 0.47 (),48 ().26 2.04 0.39 0.30 (Total Moles of Compound/ | 000 gms. of Ester) x 1 () 5 (.7 ().2 (),3 ().26 12 18 ().7 ().3 0.5

EXAMPLES 30-33 catalyst which is employed in preparing the haloge A 5-liter flask equipped with a condenser, stirrer, 35 nated phthalic anhydride. thermometer, distillation column and nitrogen sparge The Examples in Table VI illustrate the utility of the tube was charged with the designated quantities of complex employing acid anhydrides for the preparation ethylene glycol, diethylene glycol and adipic acid. The of polyesters. flask was vacuum purged twice and then sparged with a Table IV nitrogen. The flask was then heated to 140 Centigrade Examples at which temperature water began to distill off. The temperature was gradually raised to 220-225 Centis Components, gms, 34 35 grade with constant water removal. When the column E. glycol head temperature dropped to 70-75° Centigrade, Yac 4.5 E. glycol 40) uum of about 10 mm mercury pressure was applied. Adipic Acid 588 684 Water continued to be removed as required by a drop Shiphthalic 340 of head temperature. When the acid number of the Tetrabromophthalic 863 reactionfi mixture reached about 16, the designatedirr Compoundanhydride C/2A C/2A compound was added. Heating was continued with so cMOOG concentration additional water removal until an acid number of less E. 1000 I, of 0.20 23 than 0.5 was achieved. The polyesters were cooled to E a 0.23 100° Centigrade and discharged from the reaction ves- E. Number 0.48 0.5 sel. The results in Table III illustrate the efficiency of SES to the complexes in reducing the time cycle of the polyes- ss (INEGI.R.S. 12 6 ter reaction. Table III Examples EXAMPLES 36-37 Components, gms. 30 3. 32 33 so The procedure using the equipment of Examples Ethylene glycol 426 200 - 30–33 was employed in the preparation of another type Diethylene glycol w 35() 350 of polyester. The reactants and concentrations are CompoundAdipic Acid 2467- CF2A24.67. 162)A CF2A620 listed ina Table V below. (Moles of compound/ 1000 gms, of Polyester) Table V x O' 0.34 .84 ().26 65 Examples Properties a Acid Number 0.48 0.48 0.47 ().39 Components, gms, 36 37 Cycle time required w to achieve final Tetraethylene glycol 830 83) 4,020,010 9 10 transesterification catalyst than are either the stannous Table V-continued octoate or the tetrabutyl titanate alone. Examples Table VII Components, gms. 36 37 5 Examples Trimethylolpropane 575 575 Adipic acid 625 625 42 43 44 45 Compound w C/2A Compound Concentration Compound w A C CI2A (moles/1000 gms. of Moles of Compound/ Polyester) x () 0.46 OOO g", f 6 7 Properties ester ww. r Acid Nunher 0.46 ().36 ) % Free Ethylene Cycle time required to Glycol after achieve final acid 5 min. 0.88 0.86 ().79 ().7 number, hrs. 15 9 5 ().7 0.67 0.43 0.47 3) 0.71 0.55 0.43 ().39 6) 0.53 ().51 ().32 0.32 20 0.44 ().39 ().30 ().26 15 8() 0.30 ().39 ().30 0.26 EXAMPLES 38-41 The products of Examples 38-41 were prepared in a one-liter, three-necked flask equipped with a con The embodiments of the invention in which an exclu denser, stirrer, manometer, nitrogen gas sparge tube, sive property or privilege is claimed are defined as stirrer and Dean-Stark tube. The flask was charged '' follows: with 390 grams of 2-ethyl hexanol (3 moles), 148 1. The method of preparing complexes comprising grams of phthalic anhydride (1 mole), and 2 grams of mixing a tetraalkyl or tetraaryl titanate compound hav the compound as designated below. The reaction was ing the formula Ti(OR), wherein R is a radical selected conducted at a temperature of 205 Centrigrade. The from the group consisting of an aliphatic radical having extent of the reaction was determined by measuring the 25 from 1 to 18 carbon atoms, an alicyclic radical having water collected in the Dean-Stark tube. The results of between 1 and 3 rings, between 5 and 6 carbon atoms Examples 38-41 in Table VI indicate that the tin per ring, and between 5 and 18 carbon atoms per mole titanium complexes are more efficient catalyst than the cule, and an aromatic radical having between l and 3 tin catalyst alone in the preparation of esters. rings and between 6 and 18 atoms per molecule, with a 30 stannous carboxylate having the formula Table VI Time Moles Required Compound/ for 100 O Example 1000 gms. Reaction, N. Compound Ester x () min. 35 Sn VOCR'), 38 CF2A 44.0 60 39 D12A 47.0 64 4. EF2A 37.) 60 wherein R' is an organic radical having from 1 to 18 4. A 126 >92 carbon atoms in a mole ratio from 1:1 to 1:8 titanate to stannous carboxylate and stirring the mixture until 40 substantially all the titanate has reacted with the stan nous carboxylate to form said complex. EXAMPLES 42-45 2. The method of claim 1 wherein the tetraalkyl tita A one-liter flask equipped with condenser, stirrer, nate is selected from the group consisting of tetraiso thermometer and heating mantle was charged with 400 propyl titanate and tetrabutyl titanate and the stannous grams of poly(ethylene glycol adipate) polyester. The 45 carboxylate is selected from the group consisting of polyester which was prepared in the absence of any stannous octoate and stannous oleate. catalyst had an approximate molecular weight of about 3. The method of claim 1 wherein the mole ratio of 2000, an acid number of 0.37 and contained 0.17% titanate to carboxylate is from about 1:2 to 1:4. free ethylene glycol as measured by gas chromato 4. The composition produced by the method as graphic analysis. One percent (4 grams) of ethylene 50 claimed by claim 1. glycol was added to the flask and the mixture was 5. The composition produced by the method as heated to and maintained at 200 Centigrade during the claimed by claim 2. course of the reaction. The designated compound was 6. The composition produced by the method as then added to the flask and periodic samples were claimed by claim 3. withdrawn at the intervals stated below. The concen 55 7. The method as claimed by claim 1 wherein the tration of ethylene glycol was determined by gas chro reaction is conducted in the presence of an inert sol matographic procedures. The results of Table VII indi went. cate that the tin-titanium complex is a more active ck *k sk. : : 60

65