DE102006009150B4 - Process for the preparation of polytetrahydrofuran or tetrahydrofuran copolymers - Google Patents

Abstract

A process for the preparation of polytetrahydrofuran or tetrahydrofuran copolymers by polymerization of tetrahydrofuran, in the presence of a telogen and / or a comonomer on an acidic catalyst, characterized in that the reaction mixture contains from 0.001 to 5 wt .-% of at least one linear aliphatic ether.

Description

The present invention is a process for the production of polytetrahydrofuran or tetrahydrofuran copolymers with reduced functionality by polymerization of tetrahydrofuran - hereinafter called THF - in the presence of a telogen and / or comonomer on an acidic catalyst, wherein a content of linear aliphatic ethers of 0.001 to 5 wt .-% is set in the reaction mixture.

Polytetrahydrofuran - hereinafter referred to as PTHF - which is also known as polyoxybutylene glycol, is used in the plastics and synthetic fiber industry as a versatile intermediate and is used, inter alia, for the production of polyurethane, polyester and polyamide elastomers. A particularly important field of application is the production of spandex fibers. In addition, it is, as well as some of its derivatives, in many fields of application, a valuable adjuvant, for example, as a dispersant or during the decolorization (deinking) of waste paper.

PTHF is technically usually prepared by polymerization of tetrahydrofuran - hereinafter referred to as THF - on suitable catalysts. By adding suitable reagents, the chain length of the polymer chains can be controlled to adjust the average molecular weight to the desired value. The control is done by selecting the type and amount of telogen. Such reagents are called chain termination reagents or "telogens". By choosing suitable telogens, functional groups can additionally be introduced at one or both ends of the polymer chain. In industrial processes, acetic anhydride or water are often used as telogens.

Other telogens not only act as chain-termination reagents but are also incorporated into the growing polymer chain of the PTHF. Not only do they have the function of a telogen, but they are also a comonomer and can therefore be considered equally well as telogens as well as comonomers. Examples of such comonomers are telogens having two hydroxy groups, such as the diols (dialcohols). These may be, for example, ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, 1,3-propanediol, 2-butyne-1,4-diol, 1,6-hexanediol or low molecular weight PTHF. Further suitable comonomers are cyclic ethers, such as 1,2-alkylene oxides, for example ethylene oxide or propylene oxide, 2-methyltetrahydrofuran or 3-methyltetrahydrofuran. The use of such comonomers, with the exception of water, 1,4-butanediol and low molecular weight PTHF leads to the preparation of tetrahydrofuran copolymers - hereinafter called THF copolymers - and thus makes it possible to chemically modify PTHF.

For the catalytic conversion of THF with anhydrides, eg acetic anhydride, different acidic catalysts, such as acidic clays, acidic ion exchangers such as Nafion ^®, acidic metal or mixed oxides or heteropolyacids are known.

Particularly advantageous is the THF polymerization or THF copolymerization in the presence of C ₂ - to C ₁₂ carboxylic anhydrides or mixtures thereof with C ₂ - to C ₁₂ carboxylic acids such as acetic anhydride or acetic anhydride mixtures in the presence of acidic catalysts to mono- and or diesters of the PTHF or of the THF copolymers and subsequent base-catalyzed transesterification of the PTHF esters or esters of the THF copolymers with methanol to form PTHF or THF copolymers (with terminal hydroxyl groups), as described, for example, in US Pat DE-A 10245198 is described. As acidic polymerization catalysts, for example, acidic clays, acidic ion exchangers such as Nafion ^®, acidic metal or mixed oxides, or fluorosulfonic heteropolyacids contemplated.

In general, efforts are made to ensure the highest possible functionality of PTHFs. Functionality is understood as the so-called end-group functionality of the PTHF. If all ends of the PTHF molecules in the PTHF carry an OH group, the functionality is 2.000. A monofunctional alcohol such as n-butanol has the functionality of 1.000. In the reaction of PTHF with diisocyanates, the higher the functionality of the PTHF, the higher are the chain lengths. For certain applications, eg to improve the spinnability of the spinning solution in the process of spandex fiber production, however, it is desirable to make the degree of polymerization as low as possible in the reaction of PTHF with diisocyanates. To achieve this, it is known to add to the PTHF monofunctional alcohols such as n-butanol, as in the published patent application JP-A 07-278 246 is described. This also facilitates the control of the viscosity of the spinning solution (the polyurethaneurea polymer) for spandex fiber production. The exact incorporation of these monofunctional alcohols in the highly viscous polymer means a great deal of technical effort. In order to ensure the exact concentration of monofunctional alcohol in the PTHF, a separate tank with the appropriate dosing and mixing unit is usually necessary. Because of the high investment and operating costs, it is desirable to avoid the subsequent addition of monofunctional alcohols, which also increases the risk of fluctuations in the n-butanol content in the PTHF due to the high volatility of the n-butanol, uncontrolled volatilization thereof and resulting process fluctuations in the application of the corresponding PTHF advantageously reduced and to provide PTHF from the outset, which has a lower functionality than 2.

For the direct determination of the functionality of the PTHF, no methods are known from the prior art. Therefore, the functionality of the PTHF is determined by the viscosity of the spinning solutions made with this PTHF (e.g., polyurethane urea or polyurethane urea polymers in dimethylacetamide or dimethylformamide). With otherwise identical formulation, concentration and method of preparation as well as the same process conditions and other starting materials, lower viscosities of the spinning solution correspond to a lower functionality of the PTHF.

It was therefore the object to search for a process for the preparation of PTHF or THF copolymers, with the simple and economical PTHF and copolymers of THF's can be prepared with specific functionality.

We have now found a process for the preparation of polytetrahydrofuran or tetrahydrofuran copolymers having a functionality of less than two (2) by polymerization of tetrahydrofuran and in the presence of at least one telogen and / or comonomer on an acidic catalyst, the reaction mixture, via the recycling of non converted THF and / or fresh feed to reactants, 0.001 to 5 wt .-%, preferably 0.005 to 1 wt .-%, based on the reaction mixture, of a linear aliphatic ether are added.

The feed to the reactor comprises, in addition to tetrahydrofuran, telogen and / or comonomer. The linear aliphatic ether may be added to one of the starting materials or the mixture thereof. Preferably, the THF or the THF / comonomer mixture contains the linear ether. The addition of the linear ether can in principle take place in the fresh feed to the reactor or in the recovered from the workup of the polymerization products reflux of THF and unreacted linear ether, which is preferably recycled to the polymerization.

For use in the process of the present invention, linear ethers derived from linear C 1 -C 10 alcohols, e.g. Dimethyl ether, diethyl ether, methyl ethyl ether, dipropyl ether, methyl propyl ether, ethyl propyl ether, dibutyl ether, methyl butyl ether, ethyl butyl ether, propyl butyl ether, 4-hydroxybutyl-1-butyl ether, 4-hydroxybutyl-1-methyl ether, 4-acetoxybutyl - 1-butyl ether suitable. Particular preference is given to diethyl ether, methyl butyl ether, 4-acetoxybuty 1-butyl ether.

The new process makes it possible to produce high-purity PTHF with the desired functionality safely and reproducibly.

Examples of the acidic heterogeneous or homogeneous catalysts used in the process according to the invention are described below:

In the production process according to the invention for PTHF and THF copolymers, a mono- and / or diester of the PTHF or of the THF copolymers is prepared in a first step by polymerization of THF preferably in the presence of acetic anhydride and optionally comonomers over acidic, preferably heterogeneous catalysts.

Suitable catalysts are, for example, catalysts based on bleaching earths, as used, for example, in US Pat DE-A 1 226 560 are described. Bleaching earths, in particular also activated montmorillonites, can be used as shaped bodies in a fixed bed or in suspension.

Furthermore, catalysts based on mixed metal oxides, in particular groups 3, 4, 13 and 14 of the Periodic Table of the Elements, are known for the polymerization of THF. That's how it describes JP-A 04-306 228 the polymerization of THF in the presence of a carboxylic acid anhydride on a mixed metal oxide consisting of metal oxides of the formula M _x O _y with integer x and y in the range 1-3. Al ₂ O ₃ -SiO ₂ , SiO ₂ -TiO ₂ , SiO ₂ -ZrO ₂ and TiO ₂ -ZrO ₂ are mentioned as examples. Heteropolyacids, in particular H ₃ PW ₁₂ O ₄₀ and H ₃ PMo ₁₂ O ₄₀ can be used as catalysts on a support, but preferably unsupported.

The US 5,208,385 discloses catalysts based on amorphous silicon / aluminum mixed oxides. Mixed oxides based on SnO ₂ / SiO ₂ , Ga ₂ O ₃ / SiO ₂ , Fe ₂ O ₃ / SiO ₂ , In ₂ O ₃ / SiO ₂ , Ta ₂ O ₅ / SiO ₂ and HfO ₂ / SiO ₂ are also known. The aforementioned catalysts are preferably prepared by coprecipitation / sol-gel methods. Supported catalysts are in the DE-A 44 33 606 wherein tungsten or molybdenum oxides are applied to, for example, ZrO ₂ , TiO ₂ , HfO ₂ , Y ₂ O ₃ , Fe ₂ O ₃ , Al ₂ O ₃ , SnO ₂ , SiO ₂ or ZnO. Furthermore, ZrO ₂ / SiO ₂ catalysts are recommended in which the carrier has an alkali metal concentration <5000 ppm.

All cited catalysts can be used in principle as a fixed bed as well as suspension catalysts.

Catalysts based on acidic ion exchangers are known in US 4,120,903 f ÜR the polymerization of THF, especially alpha-fluorosulfonic acid-containing polymers (e.g., Nafion ^®), as described in the presence of acetic anhydride. Furthermore, catalysts containing a metal and perfluoroalkylsulfonic acid anions are suitable for THF polymerization.

In addition, other optionally activated clay minerals are known as polymerization catalysts, disclosed for example in US Pat WO 94/05719 . WO 96/23833 . WO 98/51729 . WO 99/12992 and DE-A 195 134 93 , Zeolites are also suitable as catalysts and are used, for example, in DE-A 43 16 138 described. Finally, sulfated zirconium oxides, sulfated aluminas, supported heteropolyacids and supported ammonium bifluoride (NH ₄ F * HF) or antimony pentafluoride are also known as suitable polymerization catalysts. The process according to the invention is preferably carried out with activated bleaching earths.

Catalysts based on a tellurium compound and a BF ₃ or B (C ₆ F ₅ ) ₃ complex are mentioned in European Journal of Inorganic Chemistry 18 (2003), 3314-3317. Also, BF ₃ alone or with addition of water shows catalytic activity for the reaction. Likewise, other Lewis acid compounds, namely AlCl ₃ , SbCl ₅ or SnCl ₄ , also react. Likewise, salts with SbCl ₆ , AsF ₆ , SbF ₆ as a counter anion for the use of THF in the presence of concentrated sulfuric acid are suitable. The use of fuming sulfuric acid or of SO _{3 is also} described. Furthermore, concentrated sulfuric acid with a contact based on iron acetyl acetonate or the iron salt of an organic acid can be used. Also (CF ₃ SO ₂ ) ₂ O, CF ₃ SO ₃ H, fluorosulfonic acid, chlorosulfonic acid and similar derivatives of sulfuric acid and also its salts, hydrogen fluoride, and perchloric acid are suitable as catalysts.

If a solid catalyst is used, as a pretreatment of the catalyst, for example, the drying with heated to 80 to 200 ° C, preferably at 100 to 180 ° C heated gases, such as. Air or nitrogen, in question.

The polymerization is generally carried out at temperatures of 0 to 80 ° C, preferably from 25 ° C to the boiling point of the THF. The applied pressure is usually not critical to the result of the polymerization, which is why it is generally carried out at atmospheric pressure or under the autogenous pressure of the polymerization system.

To avoid the formation of ether peroxides, the polymerization is advantageously carried out under an inert gas atmosphere. As inert gases, e.g. Nitrogen, carbon dioxide or the noble gases are used, preferably nitrogen is used.

The process can be operated batchwise or continuously, but is preferably operated continuously for economic reasons.

Since telogens lead to chain termination, the mean molecular weight of the polymer to be produced can be controlled via the amount of telogen used. Suitable telogens are C ₂ - to C ₁₂ -carboxylic anhydrides and / or mixtures of protic acids with C ₂ - to C ₁₂ -carboxylic anhydride. The protic acids are preferably organic or inorganic acids which are soluble in the reaction system. Examples are C ₂ - to C ₁₂ -carboxylic acids such as acetic acid or sulfonic acids, sulfuric acid, hydrochloric acid, phosphoric acid. Preferably, acetic anhydride and / or acetic acid are used. In the first step of the polymerization, therefore, mono- and diesters of PTHF or THF copolymers are formed. When heteropolyacids are used as the polymerization catalyst, water is generally used as the telogen, so that the polymer formed has hydroxyl groups.

The concentration of the acetic anhydride used as telogen in the polymerization reactor fed educt mixture (feed) is between 0.03 to 30 mol%, preferably 0.05 to 20 mol%, particularly preferably 0.1 to 10 mol%, based on the used THF. If acetic acid is additionally used, the molar ratio in the feed of the current polymerization is usually from 1:20 to 1: 20,000, based on the acetic anhydride used.

The mono- and diesters of the THF copolymers can be prepared by the additional use of cyclic ethers as comonomers which can be polymerized to open the ring, preferably tri-, tetra- and five-membered rings such as 1,2-alkylene oxides, e.g. Ethylene oxide or propylene oxide, oxetane, substituted oxetanes such as 3,3-dimethyloxetane, the THF derivatives 2-methyltetrahydrofuran or 3-methyltetrahydrofuran, with 2-methyltetrahydrofuran or 3-methyltetrahydrofuran being particularly preferred.

Likewise, the use of C ₂ - to C ₁₂ -diols as comonomers is possible. These may be, for example, ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, 1,3-propanediol, 2-butyne-1,4-diol, 1,6-hexanediol or low molecular weight PTHF. Furthermore, as comonomers, cyclic ethers such as 1,2-alkylene oxides, for example ethylene oxide or Propylene oxide, 2-methyltetrahydrofuran or 3-methyltetrahydrofuran suitable.

Depending on the telogen content of the polymerization mixture, mono- and / or diesters of PTHF or THF copolymers having average molecular weights of from 250 to 10,000 daltons can be produced in a targeted manner, preferably the inventive PTHF esters having average molecular weights of 500 to 5000 daltons, more preferably 650 to 4000 daltons produced. 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, the determination of which is carried out, for example, by wet-chemical OH number determination.

If a solid polymerization catalyst is used, the THF-containing effluent from the polymerization stage is filtered to retain traces of the polymerization catalyst and then fed to the distillative THF separation. However, it is also possible first to remove THF and then to remove the remaining mono- or diesters of the PTHF from catalyst residues by filtration. The second method is considered preferred. As filter devices industrially conventional layer filters are used.

The ester groups in the polymers thus obtained must be converted in a second step. A common method is initiated by alkaline catalysts reaction with lower alcohols. The transesterification with alkaline catalysts is known from the prior art and, for example, in DE-A 101 20 801 and DE-A 197 42 342 described. Preference is given to using methanol as the lower alcohol and as the effective transesterification catalyst sodium methylate.

The polymers obtained can be used by reaction with organic isocyanates in a conventional manner for polyurethane and polyurethane urea production in particular for the production of thermoplastic urethanes, spandex, thermoplastic ether esters or Copolyetheramiden. The present invention therefore further provides for the use of the polytetrahydrofuran or the tetrahydrofuran copolymers prepared by the process according to the invention for the preparation of polyurethane polymers or polyurethane urea polymers, as used, for example, for producing elastic fibers, also called spandex or elastane, thermoplastic polyurethane (TPU) or of Polyurethane cast elastomers (Cast elastomers) are needed.

In a conventional manner, PTHF or a THF copolymer is first reacted with an organic diisocyanate in excess and then with an organic diamine as described, for example, in US Pat JP-A 07-278 246 is described.

The invention will be explained in more detail with reference to examples.

Examples

example 1

Preparation of a spinning solution (polyurethane polymer)

PTHF prepared according to the following inventive examples 2 and 3, or according to Comparative Example 1, was mixed with 4,4 'diphenylmethane diisocyanate in a molar ratio of 1: 1.62 and heated in a glass flask for at 90 ° C. After 45 minutes, the prepolymer obtained was cooled to 30 ° C and treated with as much N, N dimethylacetamide (DMAC) that a 45 wt .-% solution was formed (solution A)). For chain extension, a 1.9% strength by weight solution of a mixture of ethylenediamine (EDA), 1,2-propylenediamine (PDA) and diethylamine (DEA) in DMAC was prepared. The molar ratio of EDA: PDA: DEA was 4: 1: 1 (solution B). 96 g of solution A were initially charged at 30 ° C., and 40 g of solution B were added with stirring over a period of 30 minutes. The viscosity of the resulting spinning solution was determined at 40 ° C. using a Haake VT550 SV 2. viscometer (millipaskal · second = mPas).

Example 2

19.8 g / h of THF and 3.4 g / h of acetic anhydride were in a fixed bed reactor at 40 ° C continuously over 200 mL of an acid-activated, dislocated montmorillonite catalyst as in DE-A 10245198 Example 3 is conducted. 0.2 g / h (0.85 wt.%) Of n-butyl methyl ether was added to the feed stream to the reactor. The reaction mixture was circulated through the reactor by a pump continuously in the reaction apparatus while maintaining a constant circulation: feed ratio of 50: 1. In each hour 23.4 g of fresh feed were introduced into the reactor, while the same amount of reaction product was removed from the circulation. For analysis, the volatile components of the reaction output, essentially THF and acetic anhydride and unreacted linear ether, were evaporated in vacuo at 70 ° C / 30 mbar, then at 170 ° C / 3 mbar. The polymeric residue was transesterified with methanol and sodium methylate to the diol, which removes sodium ions by precipitation with phosphoric acid and subsequent filtration. By distillation over a short path distillation at 1 mbar / 200 ° C, the PTHF was freed from lower oligomers. The molecular weight of the product thus obtained was 2055 mol / g. The polymer solution in DMAC, which was ultimately formed as described in Example 1 by further reaction as described in Example 1, had a viscosity of 63,900 mPas at 40 ° C.

Example 3

As stated in Example 2, THF was polymerized in the presence of acetic anhydride, but 4.3 wt% diethyl ether was added to the feed to the reactor. The PTHF obtained according to the procedure described in Example 2 had a molecular weight of 2036 g / mol. After conversion to the spinning solution according to Example 1, a viscosity of the spinning solution of 37500 mPas was measured.

Comparative Example 1

As described in Example 2, 20 g / h of THF and 3.4 g / h of acetic anhydride in a fixed bed reactor at 40 ° C continuously over 200 mL of an acid-activated, dislocated montmorillonite catalyst as in DE-A 10245198 , Example 3, is directed. In contrast to the examples according to the invention, the feed to the reactor was free of linear ethers. According to the procedure of Example 2, the reaction mixture was continuously circulated through the reactor by a pump in the reaction apparatus, with a constant circulation: feed ratio of 50: 1 was held. In each hour, a further 23.4 g of the reaction mixture were added to the reactor, while the same amount of reaction product was removed from the circulation. For analysis, the readily volatile components of the reaction effluent, ie essentially unreacted THF and acetic anhydride, were evaporated in vacuo at first 70 ° C./30 mbar, then at 170 ° C./0.3.3 mbar.

The polymeric residue was transesterified with methanol and sodium methylate to the diol, which removes sodium ions by precipitation with phosphoric acid and subsequent filtration. By distillation over a short path distillation at 1 mbar / 200 ° C, the PTHF was freed from lower oligomers. The molecular weight of the PTHF obtained in this way was 2024 mol / g.

The product was converted to a spinning solution as described in Example 1. The viscosity of the spinning solution at 40 ° C was 90300 mPas.

Claims (8)

A process for the preparation of polytetrahydrofuran or tetrahydrofuran copolymers by polymerization of tetrahydrofuran, in the presence of a telogen and / or a comonomer on an acidic catalyst, characterized in that the reaction mixture contains from 0.001 to 5 wt .-% of at least one linear aliphatic ether. Method according to Claim 1 , characterized in that the content of linear ether is between 0.005 and 1%. Method according to Claim 1 or 2 , characterized in that the tetrahydrofuran or tetrahydrofuran / comonomer mixture used for the polymerization contains the linear ether. Method according to one of Claims 1 to 3 characterized in that the catalyst is selected from bleaching earths, mixed metal oxides of Groups 3, 4, 13 and 14 of the Periodic Table of the Elements, supported tungsten or molybdenum oxides, heteropolyacids, acidic ion exchangers, zeolites of sulfated zirconium oxides and / or strong mineral acids Method according to one of Claims 1 to 4 characterized in that the linear ether is dimethyl ether, methyl ethyl ether, dipropyl ether, methyl propyl ether, ethyl propyl ether, dibutyl ether, methyl butyl ether, ethyl butyl ether, propyl butyl ether, 4-hydroxybutyl-1-butyl ether, 4-acetoxybutyl-1-butyl ether, 4-hydroxybutyl 1-methyl ether or mixtures thereof. Method according to one of Claims 1 to 5 , characterized in that the linear ether is diethyl ether, methyl butyl ether and / or 4-acetoxybutyl-1-butyl ether. Use of the method according to any one of Claims 1 to 6 prepared polytetrahydrofuran or tetrahydrofuran copolymers for the production of polyurethane urea polymers. Use after Claim 7 , characterized in that the one of the Claims 1 to 6 prepared polytetrahydrofuran or tetrahydrofuran copolymer for the production of thermoplastic polyurethanes, spandex, thermoplastic ether esters or Copolyetheramiden is used.