DE10110241A1 - Determining water content of solutions of Group IIIb and lanthanide compounds involves comparing areas under spectral absorption bands - Google Patents

Abstract

Absorption spectra of the solution are examined in the UV/visible region. The area ratio of absorption bands in the waveband 400-900 nm, which are influenced by water, is obtained. Water content of the solution is determined using a prior calibration curve.

Description

The invention relates to a method for determining the water content in the Rare earth salts used as catalyst components for the polymerization of Can be used.

For the homo- and copolymerization of dienes such as butadiene, isoprene, 1,3-pentadiene and in particular for the production of polybutadiene with a high 1,4-cis content (<95%), catalyst systems based on rare earths (elements of the periodic table with the atomic number 21, 39 or 57-71, in the context of this invention abbreviated with SE), in particular neodymium (US-A-3,297,667, US-A-4,444,903, EP-B1-0 007 027; EP-B1- 0 011 184; US-A-5,484,897; EP-A1-1 055 659). In order to achieve good solubility of the RE salts in aliphatic solvents such as hexane and cyclohexane, special RE carboxylates and special RE chlorides are preferred. Examples are: neodymnaphtenate, neodymium versatate, neodymium 2-ethyl-hexanoate, neodymium decanoate, and the chlorides of the type NdCl ₃ * nL, where L are ligands with donor properties such as tetrahydrofuran, i-propanol, trialkyl phosphates, sulfoxides, sulfones etc. Technically important are catalyst systems consisting of: 1. Nd carboxylates / aluminum alkyl / aluminum alkyl halides or Nd carboxylates / aluminum hydridoalkylene 7 aluminum alkyl halides (US-A-4,461,883) and 2. Neodymium carboxylates / aluminum alkylene / chlorine donors (EP-B 1-0 011 184) and 3. Neodymium chloride / triethylhexyl phosphate / aluminum alkyl (SU-726110 and SU-730710).

The chlorides are used, for example, to produce the SE carboxylates (EP-A1-0 599 096, GB-2,140,435), of the oxides or the carbonates (EP-A1-0 968 992; EP-A1-1 055 659) or of the nitrates (EP-B1-0 512 346 and WO-98/39 283-A1).  

With this procedure, the water-containing solutions of the SE- Salts in organic solvents such as cyclohexane, n-hexane or toluene. water is usually removed by azeotropic distillation. Especially with the Batch production of the SE salts are in the water content of the ver found significant differences in different batches.

The rare earth chlorides are usually made after ammonium chloride method from Taylor and Carter (M.D. Taylor, C.P. Carter, J. Inorg. Nucl. Chem., 24, 387, (1962)). The SE-III oxides are transferred by boiling concentrated hydrochloric acid in the corresponding SE trichloride oligohydrates. Then an aqueous solution of ammonium chloride (1 mol to 5-6 mol oligo hydrate) and evaporates to dryness. For the production of the anhydrous neodymium chloride, the SE trichloride oligohydrate / ammonium chloride mixture is heated under high vacuum in a tube within 30-40 h gradually from 130 ° -220 ° C. Here, ammonium chloride sublimes from the mixture Process step can also be carried out under a stream of nitrogen.

The production of anhydrous SECl ₃ using the described method is very complex and is not necessarily suitable for technical implementation. In addition, the formation of SE oxides cannot be excluded with certainty. Anhydrous SECl ₃ is practically insoluble in solvents such as hexane, cyclohexane, toluene etc. By adding ligands such as. B. tetrahydrofuran (SU-730710), ethanol (SU-675866), trialkyl phosphates (SU-675866, SU-26110 and SU-730710) and sulf oxide mixtures (SU-675866 and SU-726110) are SECl ₃ * nL which are soluble in the corresponding solvents.

SECl ₃ * nL is easier to produce if you start with water-containing SE chlorides. For this you dissolve the water-containing SE chloride in toluene and add a donor to the toluene solution such as. B. triethylhexyl phosphate or a mixture of sulfoxides and removes part of the water by azeotropic distillation. To obtain anhydrous complexes of the SE chlorides, the partially dehydrated complexes are dissolved in absolute toluene and dried over zeolite for 3-4 days (Y. Murinov, YB Monakov, ZG Shamaeva, NG Marina, VS Kolosnitsyn, YE Nikitin and SR Rafikov, Izv Akad. Nauk. SSSR, Ser. Chim., 12, 2790, 1977).

If aqueous SECl ₃ * × H ₂ O is used in the production of SECl ₃ * nL, the water must be removed more or less completely before using the RE salts as a catalyst component. The water is usually removed by reaction with dehydrating substances, e.g. B. SOCl ₂ , whereby different batches of the SE salts (as in the production of the SE carboxylates) can sometimes differ significantly in their water content. In addition, the formation of SE oxides cannot be safely ruled out with this procedure.

The influence of water has hardly been investigated in neodymium-catalyzed systems (RP Quirk et al. Polymer 41, 5903-5908, (2000)) and there is conflicting information in the literature regarding the influence of water. According to A. Pross et al. (Angew. Makromol. Chem. 211, 89, (1993)), reproducible results are only found at low water contents in the solvents used (<5 ppm), the water content in the solution of the neodymium versatate (25-700 ppm) having no influence , In contrast, Carbonaro et al. (US-A-4,736,001) that water additions up to a molar ratio Al / H ₂ O = 2/1 are favorable.

The water content of non-aqueous solutions is usually determined by titration according to Karl Fischer (E. Scholz, "Karl Fischer titration. Method for water determination." Berlin Springer Verlag 1984). This titration method can lead to unreproducible results, especially if no freshly prepared solutions are used and if the titration is not always carried out by the same person. In addition, the Karl Fischer titration cannot be used in certain cases because some additives interfere. This is the case, for example, with alkyl phosphates and alkyl sulfoxides, which are used as ligands in combination with NdCl ₃ . For these reasons, water determination by titration according to Karl Fischer can only be used in practice under certain conditions or not at all and is unsatisfactory because of the poor reproducibility of the results. In addition, the Karl Fischer titration is not suitable as a method for online determination.

An IR spectroscopic water determination in the wavenumber range 3200-3600 cm ^-1 is mentioned in the following publications: (Yu. I. Murinov, Yu. B. Monakov, ZG Shamaeva, NG Marina, VS Kolosnitsyn, Yu. E. Nikitin and SR Rafikov Bulletin of the Academy of Science of the USSR, Division of Chemical Sciences pages 2581-2582 (1978), Original submitted in Izvestiya Akademii Nauk. SSSR, Seriya Khimicheskaya No. 12, pp. 2790-2792, (1977), and (AV Kanyakin AV Petrov, EE Senderov and AI Sukhanovskaya, Zh. Anal. Kim. 21, 840 (1966). However, this reference does not show that the method described is also suitable for the water determination of RE salts IR spectroscopic water determination of solvents such as methyl ethyl ketone, amyl acetate, tributyl phosphate and pyridine in the wavenumber range 3200-3600 cm ^-1 in some cases this is only possible if carbon tetrachloride is used as auxiliary solvent. This method has the disadvantage that f For an evaluation of the spectra according to the Lambert-Beer law, in addition to the exact geometries of the sample apparatus / cuvette, the molar absorption coefficient and the concentration of the rare earths must be known.

There was therefore the technical task for the determination of water in the Salting rare earths to find a simple, versatile method that provides reproducible results and is also suitable for online analysis. Preferably this method should depend on the concentrations of the SE compounds be independent. In addition, this method should not have solutions from Chemicals are used that are not stable in storage or carcinogenic.  

It has now been found that the absorption of neodymium compounds, esp especially their salts in the UV-VIS wavelength range 400-900 nm in organic Solvents such as hexane, cyclohexane, alcohol and toluene from low water is influenced and that the absorption ratio at two wavelengths the water determination can be used regardless of the concentration of the SE salts.

The present invention therefore relates to a method for determining the Water content of solutions of compounds of elements of the periodic table with the atomic number 57-71, characterized in that the area ver ratio of two absorption bands influenced by water in the wave range 400 to 900 nm determined in a UV / VIS spectrum of said solution and the Water content determined using at least one previously determined calibration curve.

The method for water determination can preferably be used for RE salts, ie for salts of the elements with atomic numbers 21, 39 and 57 to 71, particularly preferably for carboxylates such as naphthenate, versatate, 2-ethylhexanoate, neodecanoate and for optionally with ethers such as tetrahydrofuran , Alcohols such as i-propanol, phosphoric acid esters, esters of phosphorous acid, sulfoxide-complexed halogenides, in particular compounds of the SECl ₃ * nL type, where L is an ether such as tetrahydrofuran, an alcohol such as i-propanol, a phosphoric acid ester, an ester of phosphorus Acid, which is a sulfoxide.

For the determination, solutions of the SE compounds are used in suitable solutions agents. Suitable solvents are all known to the person skilled in the art Solvents that do not have UV-VIS rays in the area of the corresponding bands absorb, such as ethanol, propanol, cyclohexane, toluene, methyl ethyl ketone, acetone as well as the corresponding solvent mixtures. The suitability of a solvent can be easily determined by a few preliminary tests.  

For the interpretation, the two bands at 580 nm and 800 nm used. It is clear to the person skilled in the art that the choice ver different RE metals, the solvents and the ligands of the compounds there are slight shifts in these bands by a few wavenumbers can. As a rule, the bands influenced by water are in the area from 500-650, in particular 550-620 nm, and 720-880, in particular 770-830 nm. By forming the ratio of the two bands, the influence of the Concentration of SE compound on water determination switched off. This is particularly advantageous.

However, it is clear to the person skilled in the art that at known concentrations of SE- Connection also a single band in this area for the determination of the Water content is suitable. This is expressly intended to be open within the scope of protection here beard invention lie.

The bands are evaluated according to their area by the area of each Band or preferably the area ratio of the two bands with one or several previously established calibration curves are compared. To list this Calibration curve / calibration curves is a water-free solution of the SE connection with be known amounts of water were added and examined by UV-VIS spectroscopy. The The area of the bands changes in a defined manner with the water content, so that in the As a rule, a continuous straight line is obtained, which serves as a calibration curve.

With the present invention, an on-line measurement is easily possible, whereby either flow cells or immersion probes are used, which depend on the flowing through the analyzing solution.

Furthermore, the use of the method according to the invention is in parallel Experimental arrangements are an object of the invention. Here, at the same time several tests carried out in parallel on a substrate or in an apparatus and analyzed. This principle is described, for example, in US-A-5,985,356 p. 3, lines 12 to  P. 4, line 59 and in US-A-6,004,617 p. 3, line 18 to page 5, line 32. Both Documents are hereby incorporated by reference for the purposes of U.S. patent practice present application added.

RE compounds, especially RE salts, are often used in technology as Catalysts used in the polymerization process of dienes. Here is the Water content is a crucial factor.

Another object of the invention is a method for homo- and co- Polymerization of dienes and optionally olefins, characterized in that that the intake flow of the SE catalytic converter is checked online for its water content becomes.

A process for the homopolymerization and co-polymerization of dienes and optionally olefins, characterized in that the inlet stream of the SE Catalyst on-line is checked for its water content, which one Area ratio of two absorption bands influenced by water in the Wavelength range 400 to 900 nm determined in a UV / VIS spectrum of said solution and the water content using at least one previously determined calibration curve certainly.

Conjugated dienes of the formula CH ₂ = CR ^a -CR ^b = CH-R ^{c are} polymerized, in which R ^a , R ^b and R ^{c are} identical or different and are a hydrogen atom, a halogen atom, an alkoxy, hydroxyl, alkylhydroxy , Aldehyde, carboxylic acid or carboxylic acid ester group or a saturated or unsaturated hydrocarbon radical having 1 to 20 carbon atoms, in particular 1-10 carbon atoms, with an alkoxy, hydroxy, alkylhydroxy, aldehyde, carboxylic acid or carboxylic acid ester group may be substituted, or R ^a , R ^b and R ^c form one or more rings with the atoms connecting them. Examples of such conjugated dienes are 1,3-butadiene, isoprene, 2-phenyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene and / or 2,4-hexadiene. Furthermore, one or more 1-olefin (s) can optionally be added in the polymerization of the conjugated dienes, such as. As ethylene, propene, 1-butene, 1-hexene, 1-octene, styrene, methyl styrene. Furthermore, the polymerization can of course also be carried out in the presence of further compounds which, for. B. can regulate the molecular weight, such as. B. hydrogen or 1,2-butadiene.

In particular, the following starting materials are polymerized:

• - 1,3-butadiene or isoprene are homopolymerized.
• - 1,3-butadiene or isoprene are co-polymerized.
• - 1,3-butadiene is copolymerized with one or more C ₃ -C ₂₀ -1 olefins, especially styrene.
• - Isoprene is copolymerized with one or more C ₃ -C ₂₀ -1 olefins, especially styrene.
• - 1,3-butadiene is copolymerized with isoprene and one or more C ₃ -C ₂₀ -1 olefins, especially styrene.

A co-catalyst is often used in addition to the SE catalyst. This As a rule, cocatalysts are aluminum alkyls and are known to the person skilled in the art. We refer to document EP-B1-0 011 184, which also applies to the For purposes of U.S. patent practice, reference is made in the present application is taken.

The invention is illustrated in the following examples.

Examples example 1

The UV / VIS absorption in the wavelength range S00 to 900 nm is determined using a UV / VIS spectrophotometer (Lambda 16 from Perkin Elmer). The measurement principle is based on the dependence of the absorption spectrum of RE salts in the wavelength range from 500 nm to 900 nm on the water content. 1, the spectrum of NdCl is exemplarily shown in Fig. In ethanol at two water contents. ₃

The anhydrous ethanolic solution of NdCl ₃ has a higher absorption at approx. 580 nm than the water-containing one, while at approx. 800 nm the water-free sample absorbs less strongly than the water-containing one.

By determining the area ratio of the absorption bands at 580 nm and 800 nm calibration curves are determined depending on the water content, whereby Fluctuations in the SE content can be eliminated within certain limits.

Example 2

Analogously to Example 1, calibration curves can be used for the determination of the water content create in SE salts.

2a) Calibration curve for the determination of the water content of 0.1 m Neodymium chloride in ethanol

To determine the calibration curves, eleven solutions of 0.1 m anhydrous NdCl ₃ in ethanol were prepared and mixed with defined amounts of water (0-10 mol water / mol neodymium).

Rolled-edge bottles with a septum lid were used for the sample production. First, the rolled rim bottles were baked in the drying cabinet at 130 ° C for one hour, sealed with a septum lid when hot and cooled under argon. 0.5 mmole (0.125 g) of anhydrous NdCl ₃ (from Aldrich) was weighed into each crimp bottle under argon and dissolved in 5 ml of absolute ethanol (from Aldrich) with shaking. Afterwards, the samples were mixed with distilled and degassed water with a micro liter syringe, so that solutions with water contents with 0-10 mol water / mol neodymium were obtained.

The absorption spectra of these samples were, as described in Example 1, the absorption spectra measured and depending on the ratio of the peak areas at 580 and 800 nm from the molar water content.

The result is shown in Fig. 2.

2b) Calibration curve for the determination of the water content of 0.1 m neodymium chloride * 3 triethylhexyl phosphate in ethanol

To determine the calibration curves, four solutions of 0.1 m anhydrous NdCl ₃ * ₃ triethylhexyl phosphate (NdCl ₃ * 3TEHP) in ethanol were prepared and mixed with defined amounts of water (0-10 mol water / mol neodymium). NdCl ₃ * 3TEHP was manufactured according to the method of Y. Murinov, YB Monakov, ZG Shamaeva, NG Marina, VS Kolosnitsyn, YE Nikitin and SR Rafikov, Izv. Akad. Nauk. SSSR, Ser. Chim., 12, 2790, 1977.

The samples were prepared in a manner comparable to that described in Example 1. The calibration curve is shown in Fig. 3.

2c) calibration curve for the determination of the water content of 0.1 m neodymium chloride * 2-triethylhexylphosphate, neodymium chloride * 3,5triethylhexylphos phate, neodymium chloride * 4 triethylhexyl phosphate and neodymium chloride * 7.5 triethylhexyl phosphate in ethanol.

To determine the calibration curves, 10 solutions of 0.1 m anhydrous NdCl ₃ * 2 triethylhexyl phosphate (NdCl ₃ * 2TEHP) in ethanol were prepared and mixed with defined amounts of water (0-10 mol water / mol neodymium chloride). For the other catalysts (NdCl ₃ * 3.5TEHP, NdCl ₃ * 4TEHP and NdCl ₃ * 7.5TEHP), the samples were prepared in the same manner as in Example 1. The catalysts were prepared using the method of Y. Murinov, YB Monakov, ZG Shamaeva, NG Marina, VS Kolosnitsyn, YE Nikitin and SR Rafikov, Izv. Akad. Nauk. SSSR, Ser. Chim., 12, 2790, 1977.

The curves are shown in Fig. 4.

2d) calibration curve for the determination of the water content of 0.5 m neodymium chloride * 3 triethylhexyl phosphate in ethanol: cyclohexane (1: 1).

To determine the calibration curves, 11 solutions of 0.05 mol / l anhydrous NdCl3 * 3 triethylhexyl phosphate (TEHP) in ethanol / cyclohexane mixtures (Volume ratio: 1/1) and with defined amounts of water (0-10 mol Water / mol of neodymium).

The samples were prepared in a manner comparable to that described in Example 1, using cyclohexane (Aldrich, bidistilled). The results are shown in FIG. 5.

2e) calibration curve for the determination of the water content of 0.05 m Neodymium versatate in ethanol: cyclohexane (2.33: 1).

To determine the calibration curves, 12 solutions of 0.05 m anhydrous neodymium versatate from Rhôn Poulenc (NdV ₃ ) in ethanol / cyclohexane mixtures (volume ratio: 1/1) were prepared and with defined amounts of water (0-10 mol water / mol neodymium ) offset.

The samples were prepared in a manner comparable to that described in Example 1 posed.

The results are shown in FIG. 6.

Example 3

With the help of the calibration curves shown in Fig. 2-6, the water content of various non-aqueous solutions of Nd salts was determined using the method from Example 1. For this purpose, a defined amount of water was added to the corresponding anhydrous solutions and the sample was measured twice independently. As far as possible, the water content was determined 3 times independently using the Karl Fischer titration. The results of both methods are compared in Table 1 below:

Table 1

Result

Table 1 shows that UV / VIS spectroscopy is suitable for determining the water content of RE salts and, in contrast to Karl Fischer titration, can also be used for RE salts of the NdCl ₃ * 3TEHP type. In cases in which the Karl Fischer titration can be used, the method according to the invention provides results which are as good as those achieved by Karl Fischer titration under optimal conditions (fresh solutions, in each case the same person).

Claims (8)

1. A method for determining the water content of solutions of compounds of the elements of the periodic table with atomic number 21, 39 or 57-71, characterized in that the area ratio of two absorption bands influenced by water in the wavelength range 400 to 900 nm in a UV / VIS spectrum of said solution is determined and the water content is determined with the aid of at least one previously determined calibration curve. 2. The method according to claim 1, characterized in that one UV / VIS spectrum the area of an absorption band in the wave range of 550-620 nm with the area of an absorption band in the wave range of 770-830 nm in relation. 3. The method according to claim 1 or 2, characterized in that the water content of solutions of neodymium salts is determined. 4. The method according to any one of claims 1 to 3, characterized in that the water content of solutions of neodymium carboxylates and neodymium chlorides, the donors to improve solubility in organic Contain solvents, is determined. 5. The method according to any one of claims 1 to 4, characterized in that the water content of said solutions at a known concentration said connections of the elements of the periodic table with the Ordinal number 21, 39 and 57-71 in the solution determined from one band only becomes. 6. Use of the method according to one of claims 1 to 5 in parallel Test arrangements.   7. Use of the method according to one of claims 1 to 5 for on-line Determination of water content of solutions of compounds of the Elements of the periodic table with atomic numbers 21, 39 or 57-71. 8. Homopolymerization and co-polymerization of dienes and, if appropriate Olefins, characterized in that the inlet stream of the SE catalyst is checked on-line for its water content, which one Area ratio of two absorption bands influenced by water in the 400 to 900 nm wavelength range in a UV / VIS spectrum Solution determined and the water content with the help of at least one beforehand determined calibration curve.