USOO7074944B2

(12) United States Patent (10) Patent No.: US 7,074,944 B2 Steinbrenner et al. (45) Date of Patent: Jul. 11, 2006

(54) METHOD FOR PRODUCING (51) Int. Cl. POLYTETRAHYDROFURAN C07D 307/77 (2006.01)

(52) U.S. Cl...... 549/429 (75) Inventors: Ulrich Steinbrenner, Neustadt (DE), (58) Field of Classification Search ...... 5497.429 Martin Haubner, Eppelheim (DE): See application file for complete search history. Achim Gerstlauer, Ludwigshafen (DE); Thomas Domschke, Speyer (56) References Cited (DE); Christoph Sigwart, Schriesheim (DE); Stefan Kashammer, Schifferstadt U.S. PATENT DOCUMENTS (DE) 5,886,138 A 3/1999 Mueller (73) Assignee: BASF Aktiengesellschaft, 6,362,312 B1 3/2002 Eller et al. Ludwigshafen (DE) FOREIGN PATENT DOCUMENTS WO 99.36459 7, 1999 (*) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 OTHER PUBLICATIONS U.S.C. 154(b) by 333 days. Tanabe et al. Studies in Surface Sci. and Catalysis, vol. 51, 108-128, 1989. (21) Appl. No.: 10/485,685 Tanabe et al..Studes in Surface Sci. and Catalysis vol. 51, (22) PCT Filed: Jul. 26, 2002 199-210, 1989. Primary Examiner Taofiq Solola (86). PCT No.: PCT/EPO2AO8340 (74) Attorney, Agent, or Firm Novak Druce & Quigg, S 371 (c)(1) LLP, Jason D. Voight

(87) PCT Pub. No.: WO03/014 189 In a process for the single-stage preparation of polytetrahy drofuran and/or tetrahydrofuran copolymers having a mean PCT Pub. Date: Feb. 20, 2003 molecular weight of from 650 to 5000 dalton by polymer (65) Prior PublicationO O Data ization of tetrahydrofurany over an acid catalvsty in the presence of at least one telogen and/or comonomer, the US 2004/O186269 A1 Sep. 23, 2004 telogen and/or comonomer is added at at least two addition points in different segments of the polymerization apparatus. (30) Foreign Application Priority Data Aug. 9, 2001 (DE) ...... 101 39 293 8 Claims, No Drawings US 7,074,944 B2 1. 2 METHOD FOR PRODUCING Known catalysts include both systems which are homoge POLYTETRAHYDROFURAN neously dissolved in the reaction system and heterogeneous, i.e. largely undissolved, systems. The present invention relates to a process for preparing It is an object of the present invention to provide an polytetrahydrofuran or tetrahydrofuran copolymers by poly economical process by means of which polytetrahydrofuran merization of tetrahydrofuran over an acid catalyst, prefer and/or tetrahydrofuran copolymers having a particular mean ably a heterogeneous acid catalyst, in the presence of at least molecular weight can be prepared in higher polymer yields one telogen and/or comonomer, wherein the telogen and/or and/or space-time yields. comonomer is added at at least two addition points in We have found that this object is achieved by a process for different segments of the polymerization apparatus. 10 preparing polytetrahydrofuran (PTHF) and/or tetrahydrofu Polytetrahydrofuran, hereinafter referred to as PTHF and ran copolymers (THF copolymers) by polymerization of also known as polyoxybutylene glycol, is used as a versatile tetrahydrofuran over a heterogeneous acid catalyst in the intermediate in the plastics and synthetic fibers industries presence of at least one telogen and/or comonomer, wherein and is employed, inter alia, for producing polyurethane, the telogen and/or comonomer is added at at least two polyester and polyamide elastomers. In addition, it is, like 15 addition points in different segments of the polymerization Some of its derivatives, a valuable auxiliary in many appli apparatus. cations, for example as dispersant or in the deinking of waste The process of the present invention makes it possible to paper. obtain PTHF and THF copolymers having a particular mean PTHF is usually prepared industrially by polymerization molecular weight in high space-time yield and at a high of tetrahydrofuran, hereinafter referred to as THF for short, conversion, with the process of the present invention being over suitable catalysts. The addition of suitable reagents able to be carried out in one stage or in two stages. However, enables the length of the polymer chains to be controlled, preference is given to the single-stage synthesis of PTHF. and the mean molecular weight can thus be set to the desired It has surprisingly been found that the cascaded addition value. Control is achieved by choice of type and amount of of the telogen and/or comonomer at at least two different the telogen. Such reagents are referred to as chain termina 25 addition points in different segments of the polymerization tion reagents or “telogens'. Selection of appropriate telo apparatus enables the space-time yield and conversion to be gens also enables functional groups to be introduced at one improved significantly. The number of addition points can or both ends of the polymer chain. be two, three, four, five or more and depends on the Thus, for example, the use of carboxylic acids or car polymerization apparatus used, in particular its type and boxylic anhydrides as telogens results in formation of the 30 capacity, and also on process engineering and economic monoesters or diesters of PTHF which subsequently have to boundary conditions. However, preference is generally be converted into PTHF by saponification or transesterifi given to using from 2 to 5 addition points. cation. These processes are therefore referred to as two-stage Examples of Suitable polymerization apparatuses are cas PTHF processes. cades of at least two tank or tube reactors, for example Other telogens act not only as chain termination reagents 35 cascades of stirred tanks, cascades of at least two fixed-bed but are also incorporated into the growing polymer chain of reactors, which may optionally be operated with circulation, the PTHF. They have not only the function of a telogen but and cascades of loop reactors. In these polymerization simultaneously act as a comonomer and can therefore be apparatuses, one segment in which an addition point for the referred to as either telogens or comonomers with equal telogen and/or comonomer is located corresponds to a tank justification. Examples of Such comonomers are telogens 40 or a tube. However, it is not necessary for each segment of having two hydroxy groups, e.g. diols (dialcohols). These the polymerization apparatus in which an addition point for can be, for example, ethylene glycol, propylene glycol, the telogen and/or comonomer is located to be a single unit butylene glycol, 1,3-propanediol. 1,4-butanediol. 2-butyne Such as a stirred tank. Rather, a reactor can be configured so 1,4-diol, 1.6-hexanediol or low molecular weight PTHF. that it fulfills the function of a plurality of reactor elements Further suitable comonomers are cyclic ethers such as 45 connected in series. It is therefore also possible to use a 1.2-alkylene oxides, for example, ethylene oxide or propy single reactor, in particular a fixed-bed reactor, which is lene oxide, 2-methyltetrahydrofuran or 3-methyltetrahydro divided into at least two, preferably from 2 to 5, segments by furan. The use of Such comonomers leads, with the excep means of Suitable internals, for example orifice plates or tion of water, 1,4-butanediol and low molecular weight sieve trays. Furthermore, it is possible to use stirred columns PTHF, to formation of tetrahydrofuran copolymers, herein 50 having more than one stage and flow tubes, each having at after referred to as THF copolymers, and in this way makes least two addition points. Particular preference is given to it possible to achieve chemical modification of PTHF. cascades of stirred tanks comprising at least two stirred In industry, use is predominantly made of two-stage tanks, preferably from 2 to 5 tanks. processes in which tetrahydrofuran is, for example, poly The telogen can be introduced into the polymerization merized in the presence of fluorosulfonic acid to form 55 either separately on its own or as a solution in the THF, with polytetrahydrofuran esters and these are Subsequently preference being given to a telogen content of from 1 to 50 hydrolyzed to polytetrahydrofuran. As an alternative, tet mol %, based on tetrahydrofuran. Comonomers can likewise rahydrofuran is, for example, polymerized with acetic anhy be introduced into the polymerization as solutions in THF, in dride in the presence of acid catalysts to form polytetrahy which case the comonomer content can be up to 30 mol %, drofuran diacetate which is Subsequently transesterified, e.g. 60 preferably 20 mol %, based on tetrahydrofuran. However, by means of methanol, to give polytetrahydrofuran. Disad the THF and the telogen and/or comonomer are preferably vantages of Such processes are that they have to be carried introduced separately into the polymerization reactor. out in two stages and that by-products such as hydrofluoric Since the telogen effects termination of the polymeriza acid and methyl acetate are formed. tion, the mean molecular weight of the PTHF or the THF The single-stage synthesis of PTHF is carried out by 65 copolymers can be controlled via the amount of telogen polymerization of THF using water, 1,4-butanediol or low used. The more telogen present in the reaction mixture, the molecular weight PTHF as telogen over acid catalysts. lower the mean molecular weight of the resulting PTHF or US 7,074,944 B2 3 4 THF copolymers. Depending on the telogen content of the Preference is given to water, ethylene glycol. 1,3-pro polymerization mixture, it is possible to prepare PTHF and panediol. 1,4-butanediol. 1.5-pentanediol, 1.6-hexanediol. THF copolymers having mean molecular weights of from polytetrahydrofuran having a molecular weight of from 200 650 to 5000 dalton, preferably from 650 to 3 000 dalton and to 700 dalton, 1.6-hexanediol, 1,8-octanediol, 1,10-de particularly preferably from 1 000 to 3 000 dalton. canediol, 2-butyne-1,4-diol and neopentyl glycol or mix The amount of telogen and/or comonomer added at each tures thereof, with particular preference being given to of the two or more addition points can be identical or water, 1,4-butanediol and/or polytetrahydrofuran having a different. At least 5% by weight of the total amount of molecular weight of from 200 to 700 dalton. telogen and/or comonomer, preferably at least 10% by Telogens used for preparing PTHF and THF copolymers weight, particularly preferably at least 15% by weight, are 10 by the two-stage method are carboxylic anhydrides and/or added after the first addition point, i.e. at the second addition carboxylic anhydride/protic acid mixtures. Preferred car point or distributed over the second to n-th addition points. boxylic anhydrides, which are derived from aliphatic or Consequently, the addition at the beginning of the polymer aromatic polycarboxylic or monocarboxylic acids, contain ization unit, i.e. at the first addition point, is not more than from 2 to 12, preferably from 1 to 8, carbonatoms. Particular 95% by weight, preferably not more than 90% by weight and 15 preference is given to acetic anhydride. The protic acids are particularly preferably not more than 85% by weight. preferably organic and inorganic acids which are soluble in The addition of the telogen and/or comonomer can be the reaction system. Preferred carboxylic acids are aliphatic controlled by setting the mean molecular weight of the or aromatic polycarboxylic and/or monocarboxylic acids PTHF or THF copolymer in each segment of the polymer containing from 2 to 12, preferably from 1 to 8, carbon ization apparatus, in the case of a cascade of stirred tanks, in atoms. Examples of aliphatic carboxylic acids are acetic each tank, via the amount of telogen and/or comonomer acid, lactic acid, propionic acid, Valeric acid, caproic acid, added in this segment so that this mean molecular weight caprylic acid and pelargonic acid. Examples of aromatic corresponds to the mean molecular weight to be achieved for carboxylic acids are phthalic acid and naphthalenecarboxy the end product. To achieve this, telogen and/or comonomer lic acid. Among these carboxylic acids, preference is given is introduced empirically, the mean molecular weight of a 25 to using acetic acid. sample is determined in a known manner, and the telogen Suitable comonomers are cyclic ethers which can be and/or comonomer addition is altered as a function of the polymerized with opening of the ring, preferably three result of this determination. membered, four-membered and five-membered rings such Apart from control via the mean molecular weight, the as 1,2-alkylene oxides, for example ethylene oxide or pro amount of telogen and/or comonomer can also be controlled 30 pylene oxide, oxetane, Substituted oxetanes Such as 3.3- so that each segment displays the same incremental produc dimethyloxetane, and the THF derivatives 2-methyltetrahy tivity based on the amount of catalyst. The productivity drofuran and 3-methyltetrahydrofuran. Particular preference (“prod') is calculated, as described below in the present is given to 2-methyltetrahydrofuran or 3-methyltetrahydro patent application, from throughput, catalyst content and furan. difference between evaporation residue (“ER”) at the inlet 35 As polymerization catalysts, it is possible to use homo and outlet of a segment. The evaporation residue can be geneous acid catalysts and heterogeneous acid catalysts. determined with Sufficient accuracy from intrinsic properties Among the Suitable homogeneous catalysts, particular men of the feed stream and the exit stream, preferably from the tion may be made of heteropolyacids. index of refraction, with the aid of a calibration curve. In the Examples of heteropolyacids which can be used as cata present context, the feed stream is the stream of reaction 40 lysts in the process of the present invention are the following mixture introduced into the segment and the exit stream is compounds: the stream of reaction mixture leaving the segment. Control dodecamolybdophosphoric acid (HPMo.On HO), of the telogen and/or comonomer addition both via the mean dodecamolybdosilicic acid (HSiMo.O.*n HO), molecular weight and via the incremental productivity dodecamolybdoceric(IV) acid (HCeMo.On HO), requires repeated Sampling, determinations and, as a func 45 dodecamolybdoarsenic(V) acid (HAsMo.On HO), tion of their results, changes to the addition. hexamolybdochromic(III) acid (HCrMoOH*n HO), If continuous control by means of the mean molecular hexamolybdonickelic(II) acid (HNiMo.OH*5 HO), weight or the incremental productivity is considered too hexamolybdoiodic acid (HJMo.On HO), complicated, it is also possible to determine a value T for the octadecamolybdodiphosphoric acid (HPMosO 11 amount of telogen and/or comonomer/segment of the poly 50 HO), merization apparatus for the respective desired end product octadecamolybdodiarsenic(V) acid (HAS.MosO25 once for each segment by means of the mean molecular HO), weight or the incremental productivity and then to add from nonamolybdomanganic(IV) acid (HMnMoO*n HO), 25 to 400% of T, preferably from 33 to 300%, particularly undecamolybdovanadophosphoric acid preferably from 50 to 200%, at each addition point. In this 55 case, the amount of telogen and/or comonomer added can be (HPMoVO*n HO), identical or different at each of the various addition points. decamolybdodivanadophosphoric acid The physical control of the telogen and/or comonomer (HPMooVO on HO), addition in the various segments of the polymerization dodecavanadophosphoric acid (HPVO*n HO), apparatus is carried out in a manner known perse by means 60 dodecatungstosilicic acid (HSiWO*7 HO), of individual pumps, valves, nozzles, orifice plates, slits, dodecatungstoboric acid (HBWO on HO), membranes, filter plates or capillary tubes. octadecatungstodiphosphoric acid (HPWO 14 Suitable telogens and/or comonomers in the preferred HO), single-stage process of the present invention are saturated or octadecatungstodiarsenic(V) acid (HASWO 14 unsaturated, unbranched or branched alpha, omega-C-C- 65 HO), diols, water, polytetrahydrofuran having a molecular weight hexamolybdohexatungstophosphoric acid of from 200 to 700 dalton, cyclic ethers or mixtures thereof. (HPMoWO*n HO). US 7,074,944 B2 5 6 Of course, it is also possible to use mixtures of het zirconium dioxide which is suitable for the process of the eropolyacids. Due to their ready availability, preference is present invention can be prepared, for example, by the given to using dodecatungstophosphoric acid, dodecamo process described in U.S. Pat. No. 5,149,862. lybdophosphoric acid, nonamolybdophosphoric acid, dode Apart from Sulfate-doped metal oxides, it is also possible camolybdosilicic acid and dodecatungstosilicic acid in the to use polymers comprising alpha-fluorosulfonic acid as process of the present invention. polymerization catalyst. Preference is given to perfluori According to the present invention, preference is given to nated polymers comprising alpha-fluorosulfonic acid which using the free heteropolyacids as catalysts, but it is also are marketed, for example, under the trade name Nafion(R) by possible to utilize their salts, in particular their alkali metal E. I. duPont de Nemours and Company and under the trade and alkaline earth metal salts, as catalysts. The heteropoly 10 names Amberlyst(R) 15 and Amberlyst(R) 36 by Rohm and acids and their salts are known compounds and can be Haas. prepared by known methods, for example by the methods Furthermore, it is possible to use mixed acid metal oxides described in Brauer (Editor): Handbuch der Präparativen of groups IIIB, IVB, IIIA to VIIIA of the Periodic Table of Anorganischen Chemie, Volume III, Enke, Stuttgart, 1981 or the Elements, in particular WO TiO, WO ZrO. the methods described in Top. Curr. Chem. 76, 1 (1978). 15 WO. SnO, MoO TiO, MoC ZrO, MoC). SnO, The heteropolyacids prepared by these methods are gen V.O., WO, TiO, TiO, SiO, ZrO. SiO, Al-O erally in hydrated form. They are preferably freed of the SiO, as are described in K. Tanabe, M. Misono, Y. Ono and coordinated water present therein before they are used in the H. Hattori, New Solid acids and Bases, Stud. Surf Sciences process of the present invention. This dehydration can and Catal. 51, in particular pages 108-128 and 199–210, advantageously be carried out thermally, for example by the Elsevier 1989, in the process of the present invention. method described in Makromol. Chem. 190,929 (1989). Suitable Supported catalysts which comprise an oxidic Preferred polymerization catalysts are heterogeneous acid Support material and oxygen-containing molybdenum or catalysts which contain acid centers having an acid strength tungsten compounds or mixtures of Such compounds as Ho of <+2 in a concentration of at least 0.005 mmol/g of catalytically active compounds and may also, if desired, be catalyst, particularly preferably an acid strength Ho of <+1.5 25 additionally doped with Sulfate or phosphate groups are in a concentration of at least 0.01 mmol/g of catalyst. described in DE-A 4433 606, which is hereby expressly Heterogeneous polymerization catalysts which can be incorporated by reference. These catalysts can be pretreated used in the process of the present invention are Supported with a reducing agent, preferably with hydrogen, as heteropolyacids, cesium salts of heteropolyacids, Sulfate- or described in DE 19641481 which is hereby expressly incor phosphate-doped metal oxides of groups IVA, VIIA and 30 porated by reference. VIIIA of the Periodic Table of the Elements, if desired Further suitable catalysts are the supported catalysts acid-activated sheet silicates or zeolites, polymers compris described in the German patent application DE 19649803, ing alpha-fluorosulfonic acids, mixed acid metal oxides of which is hereby likewise expressly incorporated by refer groups IIIB, IVB, IIIA to VIIIA of the Periodic Table of the ence, which comprise a catalytically active amount of at Elements, supported catalysts comprising an oxidic Support 35 least one oxygen-containing molybdenum and/or tungsten material and a catalytically active amount of a tungsten or compound as active composition and have been calcined at molybdenum compound or mixtures of Such compounds, from 500° C. to 1 000° C. after application of the precursor with preference being given to Supported catalysts compris compounds of the active composition to the Support material ing an oxidic Support material and a catalytically active precursor, and further comprise a promoter which comprises amount of a tungsten or molybdenum compound or mixtures 40 at least one element or a compound of an element of group of Such compounds. 2, 3 including the lanthanides, 5, 6, 7, 8 or 14 of the Periodic Suitable Supported heteropolyacids are, for example, het Table of the Elements. These catalysts generally contain eropolyacids of the formulae HPMO (dodecamolyb from 0.01 to 30% by weight, preferably from 0.05 to 20% dophosphoric acid, dodecatungstophosphoric acid) and by weight and particularly preferably from 0.1 to 15% by H-SiMO (dodecamolybdosilicic acid, dodecatungstosi 45 weight, of promoter, calculated as the Sum of its constituents licic acid), where M is molybdenum and/or tungsten, which in the form of their elements and based on the total weight are Supported on customary Support materials such as acti of the catalyst. vated carbon, silicon dioxide, on mesoporous silicon oxides The catalysts which are known from DE-A 4433 606 and grafted with sulfonic acids, as are obtained by treatment of DE 196 49 803 and can be employed according to the the mesoporous silicon oxide Supports with mercaptoalky 50 present invention generally contain from 0.1 to 50% by ltrialkoxysilanes and Subsequent oxidation, for example weight of the catalytically active, oxygen-containing com using hydrogen peroxide or nitric acid, clays, polymers or pounds of molybdenum or tungsten or of mixtures of the Zeolites such as MCM-41. Such supported heteropolyacids catalytically active, oxygen-containing compounds of these are described, for example, in T. Okuhara, N. MisZuno and metals, in each case based on the total weight of the catalyst M. Misono, Catalytic Chemistry of Heteropoly Compound, 55 and, since the chemical structure of the catalytically active, Adv. Catal. 41, 1996, Acad. Press, page 113 ff. The acid oxygen-containing compounds of molybdenum and/or tung cesium salts of the heteropolyacids described in this refer Sten is not known precisely, in each case calculated as MoO. ence, for example Css HosPWO, are also suitable for and/or WO. use as polymerization catalyst in the process of the present The German patent application DE 10032267.0 “Kataly invention. 60 sator und Verfahren Zur Herstellung von Polytetrahydrofu As sulfate-doped metal oxides of groups IVA, VIIA and ran describes catalysts which can be employed according to VIIIA, preference is given to sulfate-doped zirconium diox the present invention and comprise at least one catalytically ide and titanium dioxide, Sulfate-doped mixed oxides of iron active, oxygen-containing molybdenum and/or tungsten (III) and Zirconium dioxide and also Sulfate- or phosphate compound on an oxidic Support and in which the content of doped mixed oxides of manganese and Zirconium dioxide. 65 molybdenum and/or tungsten, based on the catalyst dried The preparation of these sulfate-doped metal oxides is under nitrogen at 400° C., is X umol of (tungsten and/or carried out by methods known per se. Thus, sulfate-doped molybdenum)/m of surface area, where 10.1ether peroxides, the polymerization lar titanium dioxide. is advantageously carried out under an inert gas atmosphere. Apart from the abovementioned polymerization catalysts, Inert gases which can be used are, for example, nitrogen, it is possible to use sheet silicates or Zeolites which may, if carbon dioxide or noble gases; preference is given to using desired, have been activated by acid treatment as heteroge nitrogen. neous catalysts in the process of the present invention. As 35 The polymerization can also be carried out in the presence sheet silicates, preference is given to using those of the of hydrogen at hydrogen pressures of from 0.1 to 10 bar. montmorillonite-Saponite, kaolin-serpentine or palygors The process of the present invention is preferably carried kite-sepiolite group, particularly preferably montmorillo out continuously, but it is also possible for it to be carried out nite, hectorite, kaolin, attapulgite, beiddellite or Sepiolite, as batchwise. are described, for example, in Klockmanns Lehrbuch der 40 The reaction can be carried out in conventional reactors or Mineralogie, 16" edition, F. Euke Verlag 1978, pages reactor assemblies Suitable for continuous processes in a 739 765. Suspension or fixed-bed mode, for example in loop reactors In the process of the present invention, it is possible to or stirred reactors in the case of a suspension process or in use, for example, the montmorillonites available under the tube reactors or fixed-bed reactors in the case of a fixed-bed trade names Tonsil R. Terrana(R) and Granosil or as catalysts 45 process. of the types Tonsil R K 10, KSF-O, KO or KS from Slid When a continuous polymerization apparatus is used, the Chemie AG, Munich. Attapulgites suitable for use in the catalyst can, if desired, be pretreated after it has been process of the present invention are, for example, marketed introduced into the reactor(s). Suitable pretreatments for the by Engelhard Corporation, Iselin, USA, under the trade catalyst are, for example, drying by means of gases, for names AttaSorb(R) RVM and Attasorb(R) LVM. 50 example air or nitrogen, which have been heated to 80–200° The term zeolites refers to a class of aluminum hydro C., preferably 100-150°C., or pretreatment with a reducing silicates which, owing to their particular chemical structure, agent as is described in DE 196 41 481 for the supported have a three-dimensional network with defined pores and catalysts which are preferred according to the present inven channels in the crystal. Both natural and synthetic zeolites tion and comprise, as active composition, a catalytically are suitable for the process of the present invention, with 55 active amount of at least one oxygen-containing molybde preference being given to Zeolites having an SiO Al-O num and/or tungsten compound. However, the catalyst can molar ratio of from 4:1 to 100:1, particularly preferably an of course also be used without pretreatment. SiO Al-O molar ratio of from 6:1 to 90:1 and very In a fixed-bed process, the polymerization apparatus can particularly preferably an SiO, Al-O molar ratio of from be operated in the upflow mode, i.e. the reaction mixture is 10:1 to 80:1. The primary crystallites of the Zeolites pref 60 conveyed from the bottom upward, or in the downflow erably have a size of up to 0.5 mm, preferably up to 0.1 mm mode, i.e. the reaction mixture is conveyed through the and particularly preferably up to 0.05 mm. reactor from the top downward. The feed mixture compris The Zeolites which can be used in the process of the ing THF and part of the telogen and/or comonomer is present invention are used in the H form. In this form, acidic introduced continuously at the first addition point of the OH groups are present in the Zeolite. If the Zeolites are not 65 polymerization apparatus. Further amounts of telogen and/or obtained directly in the H form in the process for producing comonomer are added at the second or further addition them, they can easily be converted into the catalytically points. The space velocity is from 0.05 to 0.8 kg of THF/ US 7,074,944 B2 9 10 (1-h), preferably from 0.1 to 0.6 kg of THF/(1-h) and par The productivity is in turn defined as ticularly preferably from 0.15 to 0.5 kg of THF/(1-h). Prod=ER*m(feed)/t/m(catalyst) Furthermore, the polymerization reactor can be operated in a single pass, i.e. without product recirculation, or in the where m is the massing, t is the residence time in hours and circulation mode, i.e. the polymerization mixture leaving the 5 feed refers to the reaction mixture fed into the reactor. reactor is circulated. In the circulation mode, the ratio of The number average molecular weight was then measured recirculated mixture to fresh feed is less than or equal to on the PTHF obtained in this way. The amount of butanediol 100:1, preferably less than 50:1 and particularly preferably fed in was Subsequently varied until the number average less than 40:1. molecular weight of the PTHF was 2 000+50 on three 10 Successive days. The evaporation residue and the molecular EXAMPLES weight of the PTHF were then determined. The results are shown in table 1. The invention is illustrated by the examples below. Molecular Weight Determination Comparative Example C 5 The mean molecular weight M, namely the number 15 average molecular weight defined as the mass of all PTHF 602.5g of catalyst as described in Example 1 were placed molecules divided by their amount in mol, is determined by in each reactor of a cascade of four of the atmospheric measurement of the hydroxyl number of the polytetrahy pressure glass reactors described for comparative examples drofuran. The hydroxyl number is the amount of potassium 1 to 4 and the catalyst and reactors were Subsequently dried hydroxide in mg which is equivalent to the amount of acetic at 200° C. in a stream of N. The reactors were operated as acid bound by 1 g of substance on acetylation. The hydroxyl a cascade of stirred tanks. After the catalyst had been number is determined by esterification of the hydroxyl introduced, the reactors were cooled to 60° C. and started up groups present by means of an excess of acetic anhydride. using a mixture of 1,4-butanediol in THF (tetrahydrofuran). 100% of the telogen 1,4-butanediol was added upstream of 25 the first reactor. Samples were taken daily at the outlet from the last reactor of the cascade and were freed of unreacted After the reaction, the excess acetic anhydride is hydro THF and 1,4-butanediol by heating at 120° C. at 0.3 mbar. lyzed with water in accordance with the following reaction The number average molecular weight of the PTHF equation obtained was then measured and the evaporation residue 30 after the fourth reactor was determined. The number average (CHCO)2O+HO->2CHCOOH molecular weight of the PTHF after the last reactor was 1 and backtitrated as acetic acid using sodium hydroxide. 989 g/mol. The results and the total throughputs are shown in table 1. Example 1 35 TABLE 1. Production of the Catalyst Comparative examples C 1 to C 5 Titanium dioxide (VKR 611 from Sachtleben) was cal THF 1,4-BDO cined at 500° C. in a continuous rotary tube so as to give a Comparative throughput throughput M, ER Prod material having a BET surface area of 135 m/g and a loss 40 examples (gh) (gh) (g/mol) (%) (g/kg/h) on ignition of 8.1% by weight. 73.81 kg of this titanium C 1 1 OOO 3.4 1981 4.6 19.2 dioxide were mixed in a pan mill with 29.64 kg of ammo C 2 498 2.31 2 O34 6.8 14.2 nium paratungstate, 21.73 kg of Oxalic acid dihydrate and C 3 332 1.82 2 O21 8.3 11.5 17.7 kg of water for 1 hour, extruded to form extrudates C 4 249 1.53 1 993 9.6 1O.O having a diameter of 3 mm and dried at 90° C. for 3 hours. 45 C 5 499 2.09 1989 6.7 14.0 The extrudates were subsequently calcined at 400° C. for 5 = 1,4-Butanediol hours and at 630° C. for 40 minutes. °= Number average molecular weight = Evaporation residue Continuous Polymerization of THF = Productivity 50 Comparative Examples C 1 to 4 Examples 2 to 7 A3300 ml atmospheric-pressure glass reactor which was 602.5g of catalyst as described in Example 1 were placed provided with a heating mantle and an external stirrer and in in each reactor of a cascade of four of the atmospheric which the region of the stirrer was separated from the 55 pressure glass reactors described for comparative examples remainder of the reactor by means of a wire mesh was 1 to 4 and the catalyst and reactors were Subsequently dried charged with 2410 g of catalyst as described in Example 1. at 200° C. in a stream of N. The reactors were operated as Catalyst and reactor were subsequently dried at 200° C. in a cascade of stirred tanks. After the catalyst had been a stream of N. After the catalyst had been introduced, the introduced, the reactors were cooled to 60° C. and started up reactor was cooled to 60° C. and started up using a mixture 60 using a mixture of 1,4-butanediol in THF (tetrahydrofuran). of 1,4-butanediol in THF (tetrahydrofuran). Samples were Upstream of each reactor unit of the cascade of stirred tanks, taken daily at the outlet from the reactor and were freed of the indicated proportions of the total amount of 1,4-butane unreacted THF and 1,4-butanediol by heating at 120° C. at diol were fed in by means of a metering pump. The amount 0.3 mbar. was in each case determined by means of an analytical The evaporation residue obtained in this way corresponds 65 balance. Samples were taken daily at the outlet from the last approximately to the THF conversion and is defined as reactor of the cascade and were freed of unreacted THF and ER=m(distillation residue)/m(sample). 1,4-butanediol by heating at 120° C. at 0.3 mbar. US 7,074,944 B2 11 12 The number average molecular weight of the PTHF obtained in this way was then measured. The amounts of -continued butanediol metered in were subsequently varied until the number average molecular weight of the PTHF after the last Example Reactor No. ER (%) M (g/mol) reactor was 2000+50 on three successive days. The evapo ration residue and the molecular weight of the PTHF after 5 1 1.5 1729 each reactor were then determined. The results for the 2 2.7 1758 individual reactors are reported after each example below. 3 3.9 1869 The results for the fourth reactor and the total throughputs 4 5.2 2011 are shown in table 3. 10 6 1 3.5 1874 2 5.8 1859 Example 2 3 7.8 1907 4 9.9 2 OOS In Example 2, 25% by weight of the total amount of 7 1 4.2 1873 1,4-butanediol were added upstream of the first reactor. 2 6.9 1871 Table 2 shows the total throughputs and the number average 15 molecular weight, the evaporation residue ER after the last 3 9.3 1941 reactor and the productivity. 4 11 2006 Table 2 shows the total throughputs, the number average Reactor No. ER' (%) M, (g/mol) molecular weight, the evaporation residue ER after the last reactor and the productivity. 1 5.2 3 384 2 6.6 2 631 3 7.1 2 259 TABLE 2 4 7.6 2 026 25 Examples 2 to 7 '= Evaporation residue °= Number average molecular weight Total Total THF 14-BDO throughput throughput M.’ ER3 Prod Examples (gh) (gh) (g/mol) (%) (g/kg/h) Example 3 30 2 496 3.92 2 O26 7.6 15.8 In the cascade of stirred vessels operated in example 3, 3 498 2.78 2 O12 7.9 16.4 1,4-butanediol was added in four parts, namely 40% by 4 498 2.53 2007 7.9 16.4 5 1 OOO 3.64 2011 5.2 21.7 weight upstream of the first reactor, 30% by weight before 6 332 2.03 2 OOS 9.9 13.7 the second reactor, 20% by weight before the third reactor 35 7 248 1.72 2 OO6 11.5 12.0 and 10% by weight before the fourth reactor. Table 2 shows '= 1,4-Butanediol the total throughputs and the number average molecular °= Number average molecular weight weight, the evaporation residue ER after the last reactor and = Evaporation residue the productivity. = Productivity 40 Comparison of the examples according to the present invention with the comparative examples in which the THF Reactor ER' (%) M, (g/mol) throughputs were comparable shows that higher productivi 1 3.8 2521 ties can be achieved by means of the process of the present 2 5.5 2 187 45 3 6.7 2053 invention. 4 7.9 2012 We claim: '= Evaporation residue 1. A process for the single-stage preparation of polytet °= Number average molecular weight rahydrofuran and/or tetrahydrofuran copolymers having a 50 mean molecular weight of from 650 to 5000 dalton by Examples 4, 5, 6 and 7 polymerization of tetrahydrofuran over an acid catalyst in the presence of at least one telogen and/or comonomer, In the cascades of Stirred vessels operated in Examples 4. wherein the telogen and/or comonomer is added at at least 5, 6 and 7, 1,4-butanediol was added in four parts at different two addition points in different segments of the polymer total throughputs, namely 50% by weight upstream of the 55 ization reactor or cascade of at least two polymerization first reactor, 25% by weight before the second reactor, 15% reactOrS. by weight before the third reactor and 10% by weight before 2. A process as claimed in claim 1, wherein a heteroge the fourth reactor. neous acid catalyst is used. 60 3. A process as claimed in claim 1, whereintelogen and/or comonomer is added at from 2 to 5 addition points in Example Reactor No. ER (%) M (g/mol) different segments of the polymerization reactor or cascade 4 1 2.6 1805 of at least two polymerization reactors. 2 4.4 1811 3 6.1 1892 65 4. A process as claimed in claim 1, wherein a segment of 4 7.9 2007 the cascade of polymerization reactors is a tank reactor or tube reactor. US 7,074,944 B2 13 14 5. A process as claimed in claim 1, wherein the polymer lar weight of the PTHF or THF copolymer or the produc ization reactor is a single reactor which is divided into tivity in these segments. segments by means of Suitable internals. 8. A process as claimed in claim 1, wherein polytetrahy 6. A process as claimed in claim 1, wherein at least 5% by weight of the telogen and/or comonomer are added after the drofuran is prepared from tetrahydrofuran and 1,4-butane first addition point. diol, water and/or polytetrahydrofuran having a molecular 7. A process as claimed in claim 1, wherein the control weight of from 200 to 700 dalton as telogen. parameter employed for the addition of the telogen and/or comonomer in the individual segments is the mean molecu