EP1537162A1

EP1537162A1 - Method for producing tetrahydrofurane copolymers

Info

Publication number: EP1537162A1
Application number: EP03790835A
Authority: EP
Inventors: Martin Haubner; Rolf Pinkos; Alexander Weck
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2002-08-30
Filing date: 2003-07-30
Publication date: 2005-06-08
Also published as: DE10239947A1; CN1276000C; JP4327724B2; MY135604A; US7094933B2; KR100970039B1; TWI328015B; CN1678659A; KR20050037590A; JP2005536615A; TW200406438A; AU2003251667A1; WO2004020499A1; US20060167321A1

Abstract

The invention relates to a method for the single-stage production of polyoxylalkylene glycols by the copolymerisation of tetrahydrofurane and alpha, omega diols in the presence of a heteropoly acid and a hydrocarbon. The invention is characterised in that a mixture of water and said hydrocarbon is eliminated by distillation from the copolymerisation.

Description

Process for the preparation of tetrahydrofuran copolymers

description

The present invention relates to a new process for the preparation of polyoxyalkylene glycols (polyalkylene ether glycols) by copolymerization of tetrahydrofuran and alpha, omega-diols in the presence of heteropolyacids and hydrocarbons, in which water is removed directly from the copolymerization as a mixture of the hydrocarbon.

Polyoxyalkylene glycols are important raw materials for the production of elastic fibers, elastic construction materials and coatings. They are prepared by polymerizing tetrahydrofuran (hereinafter referred to as "THF") or by copolymerizing THF with oxiranes such as ethylene oxide or propylene oxide or with alpha, omega-diols in the presence of cationic catalysts. It is known, for example, from EP-A 126 471 to use heteropolyacids as catalysts. This process makes polyalkylene ether glycols accessible in one stage, while other processes initially give the esters of polyoxyalkylene glycols which have to be hydrolyzed to give the polyoxyalkylene glycols before they can be used in the field of polymers.

When THF is copolymerized with alpha, omega-diols, water of reaction is released. In addition, the commercially available heteropolyacids contain 10 to 40 moles of water of crystallization per mole of heteropolyacid. Since water on the one hand negatively influences the catalyst activity and on the other hand acts as chain termination reagents (so-called "telogen"), it is necessary to remove the water of reaction and the water of crystallization from the copolymerization.

A batch process for the preparation of THF copolymers with alpha, omega-diols in the presence of a heteropolyacid, in which water is removed, is known from JP-A 10-87811: Part of the copolymerization solution is continuously removed from the polymerization reactor and subjected to a process for water separation. For this purpose, phase separation is first effected in a decanter and the lower phase containing the catalyst is returned to the polymerization reactor. The upper phase obtained is passed into a distillation unit in which the solid boilers are separated off. The bottom discharge, mainly copolymers, is returned to the copolymerization. The mixture is calibrated with suitable adsorption dried and also returned to the polymerization.

This discontinuous polymerization stage is very easy, but also complex and costly, since three recirculations (catalyst recycle, prepolymer recycle from evaporation and solvent recycle) are necessary to achieve a steady state. This means that a large number of devices is required.

10

The present invention was therefore based on the object of making the copolymerization of THF with alpha, omega-diols easier and more economical in the presence of heteropolyacids. In particular, a way should be found to use polyoxyal-

15 continuously produce kylene glycols with a narrow molecular weight distribution. The new process should enable polyoxyalkylene glycols with diol comonomer incorporation rates of 14 to 60% by weight, based on the copolymer. The polyoxyalkylene glycols should also have low color numbers and low residual contamination

Have 20 heteropolyacid catalyst or its derivatives.

Surprisingly, a process for the one-step preparation of polyoxyalkylene glycols by copolymerization of tetrahydrofuran (THF) and alpha, omega-diols in the presence of a

25 heteropolyacid and a hydrocarbon found, which is characterized in that water mixed with this hydrocarbon is distilled off from the copolymerization. In this application, a mixture is understood to mean a hydrocarbon-water azeotrope in addition to conventional non-azeotropic mixtures.

30 den.

The hydrocarbons used are said to be suitable for azeotroping with water. Aliphatic or cycloaliphatic hydrocarbons with 4 to

35 12 carbon atoms or aromatic hydrocarbons with 6 to

10 carbon atoms or mixtures thereof. In particular, e.g. Pentane, hexane, heptane, octane, decane, cyclopentane, cyclohexane, benzene, toluene, xylene or naphthalene, of which pentane, cyclopentane and octane are preferred and pentane in particular

40 is preferred.

The hydrocarbons are the fresh feed of the copolymerization in an amount of 1 × 10 ^{~ 4} wt .-% (corresponding to 1 ppm) to 30 wt .-%, based on the fresh feed of alpha, omega-diol and 45 THF, preferably 1 ppm to 16 % By weight, particularly preferably 1 to 10% by weight, is added. However, it is also possible to add the hydrocarbon to the top of the distillation column in order to separate the Initiate mixture of hydrocarbon and water. The respective molecular weight can be set via the total amount of water which is discharged from the copolymerization. In general, 1 mol of heteropolyacid ^" binds 10 to 40 molecules of water by coordinative binding. The heteropolyacids used as catalysts should contain about 1 to 10 molecules of water per molecule of heteropolyacid. In addition, copolymerization with the alpha, omega-used as co-monomer The higher the water content of the copolymer solution, the lower the molecular weight of the copolymer obtained.

In this application, the term “average molecular weight” or “average molecular weight” is understood to mean the number average M _{n of} the molecular weight of the polymers contained in the polymer formed.

Alpha, omega-diols such as, for example, C- to Cio-alkanediols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 2-methylbutanediol, 1,4-butanediol, 1,5-pentanediol are used as comonomers. i, 6-hexanediol, neopentyl glycol, 3-methyl-l, 5-pentanediol, 1, 8-0ctanediol, 1, 10-decanediol, diethylene glycol, triethylene glycol, low molecular weight THF copolymers with the alpha, omega-diols mentioned here with a medium Molecular weight of 200 "to 600 daltons or mixtures thereof. Low-molecular comonomers with an average molecular weight of 200 to 600 daltons and neopentyl glycol, particularly preferably neopentyl glycol, are preferably used as comonomers.

Mixtures of tetrahydrofuran, 1,4-butanediol and 2-methylbutanediol can also be used, it being possible for the proportion of 2-methylbutanediol in such mixtures to be between 100 ppm and 60% by weight, based on the mixture.

According to the invention, 1 to 60% by weight of the alpha, omega-diol, based on the tetrahydrofuran used, preferably 2 to 40% by weight, particularly preferably 3 to 20% by weight, are used in the copolymerization.

The copolymerization of the THF with alpha, omega-diols in the presence of heteropolyacids as catalysts is carried out in a manner known per se, as described, for example, in EP-A 126 471.

Heteropolyacids which are used according to the invention are inorganic polyacids which, in contrast to isopolyacids, have at least two different central atoms. Heteropolyacids arise from weak polybasic oxygen acids a metal, such as chromium, molybdenum, vanadium and tungsten, and a non-metal, such as arsenic, iodine, phosphorus, selenium, silicon, boron and tellurium as partially mixed anhydrides. Examples include the dodecotungstophosphoric acid ^" H ₃ (PWι ₂ 0 o) or the decamolybdophosphoric acid H ₃ (PMoι ₂ 0 ₄ o). The heteropolyacids can also contain actionoids or lanthanoids as the second central atom (sZ Chemie 17 (1977), pages 353 to 357 and 19 (1979), 308. The heteropolyacids can generally be described by the formula H ₈ _ _n (Y ⁿ Mi ₉ θ ₄₀ ⁾ with n = valency of the element Y (for example boron, silicon, zinc) (see also Heteropoly- and Isopolyoxomtalates, Berlin; Springer 1983). Phosphotungstic acid, phosphoromolybdic acid, silicon molybdic acid and silicon tungsten acid are particularly suitable as catalysts for the process according to the invention.

The heteropolyacids used as catalysts can be used in the copolymerization either dried (1 to 10 mol water / mol heteropolyacid) or undried (10 to 40 mol water / heteropolyacid).

The water present in the copolymerization reactor, which is partly water of crystallization from the heteropolyacid and partly water formed during the reaction, is mixed with the freshly added hydrocarbon with water at a temperature of 40 ° to 120 ° C, particularly preferably from 50 to 70 ° C. and a pressure of 150 mbar to 2 bar, preferably 230 mbar, separated off directly from the copolymerization, that is to say from the copolymerization reactor, without intermediate work-up steps such as phase separations, using a conventional distillation device.

The resulting vapor is preferably deposited in a surface condenser; however, quench and injection capacitors are also possible. The resulting condensate is fed to the solvent processing in order to remove the water. A partial return of the condensate to the reactor, i.e. dissipation of the heat of reaction by means of evaporative cooling. In order to achieve the highest possible water content in the condensate to be drawn off, a multi-stage countercurrent rectification column with the return condensate as the reflux can be inserted between the reactor and the condenser.

In a further embodiment, THF is distilled off simultaneously with the mixture of the hydrocarbon used in the copolymerization with water, which, depending on the hydrocarbon, can form a ternary azeotrope. The hydrocarbon distilled off in a mixture with water or the mixtures of water and hydrocarbon with tetrahydrofuran can be dried with a suitable solid adsorbent, for example on molecular sieves, and returned to the copolymerization. Phase separation into an aqueous phase and the hydrocarbon is also conceivable. The aqueous phase contains up to 5% by weight of THF, preferably <1% by weight. It also contains the respective hydrocarbon in concentrations of <1% by weight. THF and the hydrocarbon can be recovered and recycled by working up the aqueous phase by distillation. However, the aqueous phase can also be discarded.

The copolymer solution remaining after the hydrocarbon / water mixture has been separated off is preferably transferred to a phase separator. The heteropolyacid is separated from the product phase by adding further amounts of hydrocarbon. This process, known per se, for example from EP-A 181 621, leads to the reprecipitation of the heteropolyacid from the organic phase. The hydrocarbon already used in the copolymerization is preferably used as the hydrocarbon.

The catalyst phase remains in the reaction apparatus in a continuous mode of operation and is continuously supplemented by adding new and / or possibly recirculating the discharged catalyst in accordance with the catalyst losses which result from the discharge of small amounts of catalyst with the product-containing upper phase.

The upper phase contains the main amount of the copolymer and THF as well as small residual amounts of heteropolyacid or its secondary products. Their proportion generally does not exceed 0.03% by weight, based on the copolymerization output. Nevertheless, it was recognized that these residual amounts of the catalyst and its secondary products have to be separated off, since they adversely affect the properties of the copolymers for their further processing.

The distillation of the THF from the copolymer can be carried out before or after the removal of the catalyst components and / or secondary catalyst products by filtration, such as, for example, ultrafiltration, adsorption on solid adsorbents and / or with the aid of ion exchangers, with filtration and adsorption on solid adsorbents is preferred. The filtration is preferably carried out by distillation without prior removal of the THF. The adsorption on the solid adsorbent mentioned can also be combined with a neutralization of the polymerization output by bases. Suitable bases are, for example, the hydroxides and carbonates of the alkali and alkaline earth metals.

The adsorption is preferably carried out on activated carbon and / or metal oxides and / or ion exchangers at temperatures of 10 to 75 ° C, preferably at 20 ° C to 70 ° C. The separation in processing stage a) is particularly preferably carried out on ion exchangers and / or activated carbon. Sodium hydroxide, aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide, lanthanum oxide and / or calcium oxide are preferably used as metal oxides.

Suitable activated carbon can be obtained, for example, from Merck, Darmstadt or in the form of the commercial product activated carbon type CPG UF 8x30 from Chemviron Carbon.

Suitable ion exchangers are, for example, anion exchangers such as the commercial product Lewatit MP 600®, which can be obtained from Bayer AG, Leverkusen, mixed ion exchangers such as, for example, the commercial product Serdolit®, which can be obtained from Serva, Heidelberg, or molecular sieves Pore sizes from 3 to 10 Å.

The inventive separation of the catalyst components and / or catalyst secondary products by adsorption on solid adsorbents is preferred in a fixed bed at a load of generally 0.2 to 5 kg / l * h, in particular 0.4 to 4 kg / Ah (kg of polymerization output per 1 adsorbent per hour).

The process according to the invention can be carried out either continuously or batchwise or in a semi-batch mode. The semi-batch mode or semi-continuous mode is understood to mean that the heteropolyacid is initially charged with 20 to 50% by weight of the other starting materials. The remainder of the starting materials is then metered in over the course of the reaction time. For the continuous and discontinuous procedure, the heteropolyacid is expediently used in amounts of 10 to 300 parts by weight, preferably 50 to 150 parts by weight, based on 100 parts by weight of the monomers used (THF and alpha, omega-diols) , used. It is also possible to add larger amounts of heteropolyacid to the reaction mixture.

The heteropolyacid can be fed to the reaction in solid form, whereupon it is gradually brought into contact with the other reactants to form the liquid Catalyst phase is solvated. One can also proceed in such a way that the solid heteropolyacid is mixed with the alpha, omega-diol and / or the THF to be used and the catalyst solution obtained is passed into the reactor as a liquid catalyst phase. Both the catalyst phase and the monomeric starting material can be placed in the reactor. However, both components can also be introduced into the reactor at the same time.

In the case of continuous operation, fresh monomer is usually metered into the reactor in a controlled manner via a fill level control. Fresh monomer is expediently fed in to the extent that product and unreacted monomer are discharged from the reaction apparatus. In this way, the residence time, and hence the polymerization time, can also be controlled, so that a further means for influencing and adjusting the average molecular weight of the resulting polymer is available. In general, depending on the amount of catalyst and the reaction temperature in the batch process, the copolymerization is carried out for a period of from 0.5 to 70 hours, preferably from 5 to 50 hours and particularly preferably from 10 to 40 hours. In the continuous process, residence times of 1 to 50 and preferably 10 to 40 hours are usually set. At the beginning of a continuous reaction, the reaction system described takes a certain time until a steady state equilibrium has been reached and during which it can be advantageous to keep the reactor outlet closed, that is to say not to discharge any product solution from the reaction apparatus.

The copolymerization is usually carried out at temperatures from 20 to 100 ° C., preferably at 30 to 80 ° C. It is advantageous to work under atmospheric pressure, but the reaction under pressure, primarily under the autogenous pressure of the reaction system, can likewise prove expedient and advantageous.

The reactors should be equipped with powerful mixing devices, for example agitators, both in batch, semi-batch mode and in continuous mode.

All liquid reactors known to those skilled in the art with an inert and / or external free liquid surface for the necessary evaporation of the vapors containing water, in which sufficiently high shear forces in the liquid to suspend the catalyst phase in the homogeneous monomer / polymer phase are used as the reactor are suitable (stirred tanks, circulation reactors, jet loops, pulsed internals). A particularly favorable design is the design as a jet loop, since the necessary temperature control of the reactor can be easily integrated into the liquid circulation flow. The water-containing mixture of the hydrocarbon is evaporated continuously or discontinuously from the reaction mixture and the water content of the reactor content is thus adjusted to values which are favorable in terms of reaction technology.

The method according to the invention is advantageous under one

Inert gas atmosphere carried out, wherein any inert gases such as nitrogen or argon can be used. The reactants are freed of any water and peroxides contained therein before they are used.

However, the continuous procedure is preferably used. The reaction can be carried out in conventional reactors or reactor arrangements suitable for continuous processes, for example in tubular reactors which are equipped with interior fittings which ensure thorough mixing of the emulsion-like copolymerization batch or can also be carried out in stirred tank cascades.

An emulsion-like copolymerization approach means one with water contents of 2 to 10 mol water / per mol heteropolyacid.

According to the process of the invention, polyoxyalkylene glycols, in particular copolymers of THF and neopentyl glycol, can be obtained economically and in good yield, selectively and with a narrow molecular weight distribution and in pure form with low color numbers. The copolymers have installation rates of the alpha, omega-diol comonomer of 10 to 50% by weight, based on the copolymer, and average molecular weights M _n of 600 to 6000. The polyoxyalkylene glycols which can be prepared according to the invention are used, for example, to produce special polyurethanes which are suitable as highly elastic composite materials. A polyurethane polymer which contains the copolymers which can be prepared according to the invention has a high elongation after breakage, a slight change in tension when elongated, a low hysteresis loss when expanding and contracting and a high elasticity even in extreme cold. Examples

Determination of the W content in the polymerization discharge (cation analysis by atomic absorption spectroscopy AS)

Approximately 1 g of the sample solution is subjected to a digestion process in which the sample is first treated with concentrated sulfuric acid. After the mineral acids have been consumed, the W remains in a hydrochloric acid solution. In this solution, the tungsten content is determined by mass spectrometry with inductively coupled plasma (ICP-MS).

Determination of the color number

The polymer freed from the solvent is untreated in a liquid color measuring device LICO 200 from Dr. Measured for a long time. Precision cuvettes type no. 100-QS (layer thickness 50 mm, from Helma) are used.

Determination of the OH number

The hydroxyl number is understood to mean the amount of potassium hydroxide in mg which is equivalent to the amount of acetic acid bound in the acetylation of 1 g of substance.

The hydroxyl number is determined by the esterification of the hydroxyl groups present with an excess of acetic anhydride. After the reaction, the excess acetic anhydride is hydrolyzed with water and back-titrated as acetic acid with sodium hydroxide solution.

Determination of the copolymerization ratio

The copolymerization ratio was determined by ¹ H-NMR using a device from Bruker, device type: dpx 400; 400 MHz, log. Default:

Tetra ethylsilane (TMS) determined using the solvent CDC1.

example 1

A mixture of 5060 g of THF and 440 g of neopentyl glycol was stirred into a homogeneous solution in a 20 l double-walled reactor with a magnetic stirrer. 4125 g of a hydrated dodecaphosphorotungstic acid (H P0 ₄ ^x x H ₂ 0 with x = 4-7) were added with stirring. The temperature of the heating medium (oil) was set to 95 ° C. and the emulsion was stirred intermittently for 5 hours. 200 g / h of a mixture of neophen tylglycol / THF / n-pentane, which consists of 8 parts of NPG, 3 parts of pentane and the rest of THF, continuously added to the reaction vessel. The reaction temperature is kept at 63-64 ° C. The THF7 pentane / water mixture which evaporated was condensed and worked up.

The continuously obtained reaction discharge from the polymerization reactor was mixed with 250 g of pentane in a work-up vessel and phase separation was brought about. The heavy, aqueous phase was returned to the polymerization vessel. The upper phase was passed at 20 ° C. over activated carbon (Chemviron Carbon; type CPG UF 8 x 30), which was arranged in a 2.5 1 container as a fixed bed.

450 g / h of the reaction effluent treated with activated carbon and 210 g / h of the condensate evaporated from the reaction (% by weight: 97 THF, 0.2 pentane, 1.9 water) were at stage 7 equipped with 30 theoretical stages, operated at 1.2 bar operated countercurrent rectification column and there under a reflux of 1105 g / h (% by weight: 0.1 THF, 1 water, 98.8 pentane) into a vapor stream of 1210 g / h (% by weight : 98.3 pentane, 0.09 THF, 1.5 water) and a bottom stream of 553 g / h (% by weight: 70 THF, 7.3 neopentyl glycol, 22.5 copolymer, 0.1 pentane). The top stream was condensed, forming two liquid phases. The water phase was partially removed (57.3 g / h, pentane and THF contained only in traces). The remaining water phase and part of the organic phase were added to the column as reflux. Pentane losses were supplemented in a return pentane stream for reaction and phase separation. To adjust the water content in the reaction or phase separation, part of the water phase was possibly introduced into the back pentane stream.

From the bottom discharge from the column, the THF was first evaporated in one stage at 1.2 bar and 75 ° C. and returned to the reaction, and then the NPG was likewise evaporated in one stage at 15 mbar and 170 ° C. and returned to the reaction.

A copolymer with an OH number of 58 mg KOH / g, a color number of 10 APHA and a W content of <1 ppm was obtained.

The installation rate of NPG was 18 parts by weight. Example 2: Discontinuous process control

The reaction apparatus consists of a distillation device which has a 50 cm distillation column, a condenser and reflux valves, and a heatable 10 1 reactor.

765 g of neopentyl glycol and 1875 g of THF are added to the reactor and stirred to give a homogeneous solution. 1500 g of hydrated dodecaphosphorotungstic acid (HP0 ₄ * 12 Wo ₃ * x H0 with x = 4-7, from Aldrich) were added with stirring. The temperature of the heating medium was set to 95 ° C. After the temperature of the reaction solution reached 70 ° C, the emulsion-like solution was refluxed for 5 hours,

50 ml of pentane were then added via the top of the distillation column. The water liberated during the reaction was distilled off together with THF. A pentane / water mixture which had the azeotropic composition at the top of the column was formed in the column. The top stream was condensed. A two-phase mixture was formed, the upper organic one

Phase was returned to the column. The reaction time was 24 hours. 122 g of water were distilled off.

After the reaction, the separate solution phase (2700 g) was removed. Thereafter, 1300 g of catalyst phase remained. The solution phase was worked up analogously to Example 1. The OH value of the copolymer was determined. The molecular weight of the polymer was 1929. The copolymerization ratio of neopentyl glycol was determined by means of ¹ H-NMR and was 34.5 mol%.

Claims

claims

1. A process for the one-stage preparation of polyoxylalkylene glycols by copolymerization of tetrahydrofuran and alpha, omega-diols in the presence of a heteropolyacid and a hydrocarbon, characterized in that water in the mixture with this hydrocarbon is distilled off from the copolymerization.

2. The method according to claim 1, characterized in that an aliphatic or cycloaliphatic hydrocarbon with 5 to 12 carbon atoms or an aromatic hydrocarbon with 6 to 12 carbon atoms or mixtures thereof are used.

3. The method according to any one of claims 1 or 2, characterized in that pentane is used as the hydrocarbon.

4. The method according to any one of claims 1 to 3, characterized in that tetrahydrofuran is distilled off at the same time.

5. The method according to any one of claims 1 to 4, characterized in that the mixture of hydrocarbon, water and optionally tetrahydrofuran are distilled at 40 to 120 ° C and a pressure of 150 mbar to 2 bar.

6. The method according to any one of claims 1 to 5, characterized in that the hydrocarbon or the hydrocarbon / tetrahydrofuran mixture is returned after drying.

7. The method according to any one of claims 1 to 6, characterized in that the method can be carried out continuously or discontinuously.

8. The method according to any one of claims 1 to 7, characterized in that neopentyl glycol is used as the alpha, omega-diol.