DD154610A1 - METHOD FOR PRODUCING LOCAL ORGANODILITHIUM POLYMERIZATION INITIATORS - Google Patents

Abstract

The invention relates to a process for preparing organodilithium polymerization initiators obtained by reacting lithium with conjugated dienes in the presence of polycyclic aromatic hydrocarbons in certain solvent mixtures. The Dilithiumorganoverbindungen are completely soluble in the reaction medium and the solutions have a high content of carbon-bonded lithium and a high stability against degradation. The process requires only short reaction times with high lithium conversion and ensures the formation of products containing 2 to 6 diene units per 2 lithium atoms. To prepare the stable solutions of the dilithium organo compounds, only one process stage is required and the reaction can be carried out at room temperature using lithium in the form of pieces or wire.

Description

applicant:

VEB Chemical Works Buna

Authorized Representative: Dr. med. Harry Schlief in the VEB Chemical Works Buna 4212 Schkopau

Title of the invention

Process for the preparation of soluble organodilithium polymerization initiators

The invention relates to a process for the preparation of soluble OrganodilithiuM polymerization initiators of substituted or unsubstituted conjugated dienes, which are suitable for the homo- or copolymerization of anionic polymerizable monomers, in particular of conjugated dienes and vinyl-substituted aromatic compounds for the preparation of telechelic polymers and a high stability have.

Char akteristik the known solutions tec hnischen

It is known that oligomeric dienyldilithium compounds containing 2 to 10 monomer units per molecule are used as initiators for the "living" polymerization of conjugated and / or vinyl-substituted aromatic compounds. These initiators generally require a polar diluent in their preparation since they can not be prepared in low dielectric constant solvents.

3.SEr ⁰ j97 '/' * iüi].,?;:

m 2 -

2 0 0 9 8 2

They are generally prepared by reaction between lithium metal and a conjugated diene in the presence of a polycyclic hydrocarbon in certain ethers, such as. As tetrahydrofuran, dimethoxyethane or diethyl ether, which allow the solvation of the cations obtained. In all known processes, the ethers used are used in at least stoichiometric amounts with respect to the lithium metal in order to achieve reasonable yields of organodilithium compound and to keep the initiator in solution.

However, dilithium polymerization initiators are so unstable in polar solvents that they can not be stored for a long time after preparation without undergoing significant loss of their initiator activity (DT-OS 2,003,384, U.S. Patent 3,388,178).

The durability of organolithium compounds is z. B. in tetrahydrofuran at room temperature for only 2 hours »In mixtures of tetrahydrofuran and inert solvents, they react with tetrahydrofuran with decomposition (Liebigs Ann. Chem. 74-7 (1971), p 70-83).

It has already been proposed in DT-OS 1 817 4-79 and US-PS 3 377 404, oligomeric Dienyldilithiumverbindungen in polar solvents, such as. As tetrahydrofuran or diethyl ether, herzusülen and then the polar solvent by a non-polar solvent such. As η-hexane, cyclohexane, benzene or toluene, to replace »

The disadvantages of this method are that two stages are required to prepare the initiator and replacement of the solvent by another leads to increased operating costs.

A v / Eiterer disadvantage is that the conditions which are required for the removal of the _ether} often benreaktionen can lead between your dilithium initiator, and the ether to N _e, having a part v / else deactivation of the initiator result, so that the This is especially important when the initiator is used for the preparation of block copolymers of type ABA or of telechelic polymers.

In US-PS 388 178 and DT-AS 1 768 188 solutions of dilithium isoprene dimers in benzene, which have a stability of 1 to 2 months, when stored at low temperatures _{5 are} described. These solutions are prepared by adding to a mixture of a Lithiuiridispersion in mineral oil, dimethyl ether and benzene at low temperature (-20 to -30 C) with the conjugated diene, removed the dimethyl ether, adding more benzene, the reaction mixture to 30 to 35 0 heated and filtered from unreacted lithium. The catalyst used is a benzene-dissolved adduct of lithium and a conjugated diene. »

The resulting solutions contain from 20 to 30 parts by volume of dimethyl ether based on the total volume of organic solvent. Solutions with a concentration of the adduct of 1.5 mol / l of benzene can be prepared, but solutions with a concentration of 1 mol / l and less should have greater stability over longer periods of time.

In addition to the lack of solvent exchange already mentioned above, these solutions according to DT-OS 2,148,147 have the further disadvantage that they are very viscous and contain some undissolved product, which is conjugated with a view to use as a catalyst for the homogeneous anionic polymerization of Dienes and vinyl-substituted aromatic monomers is detrimental «

2 0 0982

For solubilization, it is necessary to effect a chain extension of the dilithium organo compound by the addition of a small amount of a conjugated diene in a 3 × process stage.

In DT-OS 2 14-8 147 and FR-PS 2 154 978 a modified procedure is described, wherein Dilithium-Dienyloligomere be prepared analogously to US-PS 3,388,178 in dimethyl ether. When the dimethyl ether is replaced by a non-polar solvent, the initiator solution becomes a weakly solvating arylalkyl. Diaryl ether or a tertiary amine, such as. As anisole, dimethylaniline or triethylamine, added, whereby the dimethyl ether can be removed at low temperatures, so that the known heat decomposition reactions are prevented. This process is uneconomical due to the cost of the aromatic ethers and gives rise to difficulties in separating the high boiling ethers from the final product.

All known processes also require long reaction times for preparing the dilithiura-dienoyl oligomers or for removing the ether used as reaction medium. Another disadvantage of an economical design of the process are the low reaction temperatures and the required use of a lithium dispersion with a certain particle size to achieve satisfactory lithium urate yields.

According to the prior art, the polycyclic aromatic hydrocarbons used as activators, such as. As naphthalene, in stoichiometric amounts, which are equivalent to the lithium used, needed, which affects the usability of the lithium-diene adduct solutions. , ·

Object of the invention

The aim of the invention is »to eliminate the disadvantages of the known processes and to allow the dilithiation of conjugated dienes in a simple, smooth reaction in one step at short reaction times and relatively high reaction temperatures without process engineering difficulties.» High yields and a high concentration of Initiatorlösungen be dilithium compound and 'high stability against degradation guaranteed.

Explanation of the essence of the invention

The invention has for its object _$ to develop an improved process for the preparation of highly concentrated solutions dilithium Dienyloligomerer containing and 2 to β monomer units per molecule, the conjugated as initiators for the anionic polymerization of dienes and vinyl substituted aromatic compounds to telechelic polymers suitable " which, moreover, meets the above requirements.

The object is achieved in accordance with the invention by reacting lithium and a conjugated diene in the presence of a polycyclic aromatic hydrocarbon in a toluene / tetrahydrofuran or diethyl ether / tetrahydrofuran mixture as the reaction medium.

The conjugated dienes useful in this invention are 1,3-conjugated dienes containing 4-12 carbon atoms per molecule, such as 1,3-butadiene, isoprene or 2 _{ 3-dimethyl-1,3-butadiene.

The lithium can be used in any form, such as, for example, as wire _s pieces or in a finely divided state, with good results being achieved with sturdy lithium equal. The applicable amount of lithium is 0 _? 5-1.5 g atoms per mole of diene

-6- 200982

The polycyclic aromatic hydrocarbons to be used as activators are preferably naphthalene, anthracene or diphenyl. The activator promotes adduct formation and retards polymerization of the diene. However, its M _s length should be kept as low as possible. In the process according to the invention, 0.005 to 0.125 mol per g-atom of lithium suffice.

In the preparation of Dilithiumorganoverbindungen a toluene / tetrahydrofuran or a diethyl ether / tetrahydrofuran mixture is used as a solvent. The amount of solvent is not critical, but 5-10 moles of solvent per mole of diene are used to achieve high concentrations of dilithium compound while maintaining solubility. The tetrahydrofuran is used in amounts of 5-30 vol .-% based on the total volume of solvent. The reaction temperature can be between -30 and + 50 C and is preferably +10 to + 30 ° C. The reaction time is 1-3 hours.

The process according to the invention can be carried out under pressure or without pressure. A preferred form of the process according to the invention is carried out as follows:

The activator, lithium and purified and dried solvent mixture are placed in an inert gas atmosphere. Within 1-2 hours to the reaction mixture, the conjugated diene is metered in at atmospheric pressure continuously ♦ 'The liquid at normal pressure and room temperature conjugated dienes are added as a solution in the appropriate solvent mixture, butadiene as a gas or in the liquefied state. The reaction temperature is 20-25 G. After completion of the reaction, the unreacted lithium, which can be reused for further reactions, is filtered off.

The resulting dilithium dienoyl oligomers contain 2-6 monomer units per molecule and are completely soluble in the solvent mixture. The Lithiumurasatz is 80-90% _t based on the used metallic lithium, of which 90-95% in terms of the polymerization-C-Li bond present "

The solutions have a concentration of 1.6 to 2.6 g atoms of lithium per liter and can be stored for a period of 2-4 weeks without suffering a loss of their initiator activity when stored at temperatures below +5 C takes place in an inert gas atmosphere »

According to the invention, in a one-stage process, concentrated »stable solutions of lithium lithium diisithium compounds and 1,3-dienes with high initiator activity are obtained * '

The invention is further distinguished by the fact that the dilithium dienoyl oligomers can be prepared from readily available and relatively inexpensive starting materials by using molar amounts of lithium in lump form and small amounts of activator, and also in short reaction times and relatively high temperature in good yield ,

The invention will be explained in more detail by the following examples:

Example 1:

6.3 g of lithium in the form of pieces, 7.68 g of naphthalene and 24-0 ml of toluene and 60 ml of tetrahydrofuran are charged into an argon-flushed reaction flask equipped with stirrer, thermometer and dropping funnel. From the dropping funnel, a solution of 40.8 g of isoprene in a mixture of 120 ml of toluene and'30 ml of tetrahydrofuran is added dropwise within 2 hours. The temperature is kept at +25G. The reaction starts immediately. After completion of the reaction, unreacted lithium is filtered off.

2 0 0982

The resulting solution has a lithium concentration of 1.8 equivalents per liter. This corresponds to a lithium conversion of 90 % · The activity (content of carbon-bound lithium) is 96 %,

Example 2:

Example 1 is repeated, but instead of the toluene / tetrahydrofuran mixture a Diathyläther / tetrahydrofuran mixture with 10 vol .- $ tetrahydrofuran is used. The lithium conversion is bö / o, the concentration of lithium 1, A5 equivalents per liter and the activity 95, 4 35.

example 3 :

9.6 g of naphthalene, 4.2 g of lithium and a mixture of 150 ml of toluene and 50 ml of THF were placed in the reaction flask. 40 g of gaseous butadiene were introduced with stirring at 20 ° C. within 2 hours. After complete addition of butadiene was stirred for a further 1 hour and then unreacted lithium filtered off. The lithium conversion was 85 %. The solution had a lithium concentration of 2, 7 equivalents per liter and an activity of 96 % .

Example 4:

To 1.57 g of lithium in the form of pieces, 1.92 g of naphthalene, 60 ml of toluene and 15 ml of tetrahydrofuran, a solution of 12.3 dimethylbutadiene in 30 ml of toluene and 7.5 ml of tetrahydrofuran within 1.5 hours at 25 C added dropwise. After completion of dimethylbutadiene addition is stirred for a further 30 minutes and then filtered the solution. The solution has a lithium concentration of 1.6 equivalents per liter and an activity of 94 % at 80% lithium conversion.

Claims (3)

Claim for invention 1 »Process for the preparation of soluble organodilithium ~ poly ~ lysis initiators by reaction of lithium with conjugated dienes in the presence of polycyclic aromatic compounds
Compounds and ethers, characterized in that O ₉ 5
to 1 _S 5 g Atorne Lithiümstücke per mole of diene in 5 to 10 moles
a solvent mixture from 70 to 95% by volume of toluene or diethyl ether and 5 to 30 % of tetrahydrofuran in the presence of
'0.005 to Oj'125 moles of the polycyclic aromatic compound per equivalent of lithium are reacted with the conjugated diene having 4 to 12 C atoms per molecule at temperatures of 10 to 30 C for at least 1 hour. 2. The method of item 1, characterized _s that the polycyclic aromatic compounds are preferably naphthalene, anthracene or biphenyl. 3 * Method according to item 1 and 2, characterized in that the conjugated dienes are 1j3-butadiene, isoprene or 2 _t 3-dimethyl-1,3-butadiene.