CS209257B1 - Preparation method of soluble organodilithium polymerization starting catalyst - Google Patents

Description

The invention relates to a process for the preparation of soluble organodilithium polymerization initiators obtained by reacting lithium with conjugated dienes in the presence of polycyclic aromatic compounds and ethers. [

It is known, . The oligomeric dienyldilithium compounds having 2 to 10 monomer units in the molecule can be used as initiators for the preparation of "living" polymers from conjugated or [vinyl-substituted aromatic compounds]. These initiators require their preparation to be carried out mostly in the presence of the polar They cannot be prepared in solvents with a low dielectric constant. They acquire; with all the reaction between metal · lithium and conjugate! diene in the presence of a polycyclic hydrocarbon in certain ethers, such as tetrahydrofuran, dimethoxyethane or diethyl ether; allow solvation of cations. In all known processes, the ether is used in at least a stoichiometric amount, based on the lithium metal, in order to reduce the amount of ether. has reached a reasonable yield of the organodilithium compound. ·

Dilithium polymerization initiators, however, are so unstable in polar solvents that, after preparation, they cannot be stored for an extended period of time without substantially losing their activity (NSR-OS 2 003 384, U.S. Pat. No. 3 388 178). . Durability organo209257 ¹ - ж lithium compounds, e.g. in tetrahydrofuran at room temperature for only 2 hours. Also mixtures of inert solvents tetrahydrofuran and reacted with tetrahydrofuran - and extend (Liebig. Ann. Chem. 747 (1971), pp. 70- 83).

It has already been described in NSR-OS 1 817 479 and U.S. Pat. No. 3,377,404 to prepare oligomeric dienyldilithium compounds in polar solvents such as tetrahydrofuran or diethyl ether and to replace the polar solvent with a non-polar solvent such as n. -hexane, cyclohexane, [benzene or toluene. |

The disadvantage of this method resides in the fact that ^'the pnpravě mictétorp ^- are ^- Abortion ^b and ^d va ^- s ^t u i ^p not replacement solvent increases production costs. Another disadvantage is that the conditions necessary to remove the ether can - often lead to side reactions between the dilithium initiator - and the ether which - result in partial deactivation of the initiator, so that the resulting mono and dilithium solutions also contain inactive initiator molecules. This is particularly important when the initiator is used to prepare ABA-type block polymers or to prepare telechelic polymers.

U.S. Pat. No. 3 388 178 and NSR-AS-1 768 188 disclose dilithium isoprendimers solutions in benzene having a stability of 1-2 months when stored at low temperatures. These solutions are prepared by reacting a mixture of lithium dispersion in mineral oil, dimethyl ether and benzene with a conjugated diene at low temperature of -20 to -30 ° C, removing the dimethyl ether and adding further benzene, whereupon the reaction is carried out. the mixture is heated to 30-35 ° C and filtered off unreacted lithium. The catalyst is used. a lithium conjugated diene adduct dissolved in benzene.

The resulting solutions contained 20 to 30 volume% dimethyl ether based on the total volume of organic solvents. They will. solutions having an adduct concentration of 1.5 mol / l benzene are prepared, but solutions having a concentration of 1 mol / l or less show greater stability over a longer period of time.

In addition to the above-mentioned disadvantages of confusion of - according to NSR-OS ΐ 2 148 .147 have the further disadvantage that - they contain a bit. of the undissolved product, which is disadvantageous due to their use as a catalyst for homogeneous anionic polymerization of conjugated dienes and vinyl-substituted aromatic | - monomers. The solubility must be influenced by the third stage, where the chain of the organo-dilithium compound is extended by adding a small amount of conjugated diene.

German-OS 2,148,147 and FR 2,154,978 disclose an I-modified process in which dilithium dienes | The oligomers are prepared analogously to U.S. Pat. No. 3,388,178 in dimethyl ether. To replace dimethyl ether with a non-polar solvent, a slightly solvating arylalkyl ether or diaryl ether is added to the initiator solution I. or a tertiary amine such as anisole, dimethylaniline or triethylamine, whereby the dimethyl ether can be removed at deeper temperatures so that decomposition can be prevented. This process is uneconomical in terms of the cost of the aromatic ether and causes difficulties in separating the high-boiling ether from the final product.

In addition, all known processes require a long reaction time to obtain the dilithium-dienyloligomers, possibly to separate the ether used as reagent. Unsuitable for the economy In addition, the deep process reaction temperatures as well as the use of lithium dispersions with a certain particle size are required in order to achieve satisfactory lithium conversions. and

I According to known methods, polycyclic aromatic hydrocarbons, such as naphthalene, used as activators, must be added in stoichiometric amounts equivalent to those used. lithium, which impairs the utility of lithium-1 ' -diene adducts. and

It is an object of the present invention to overcome these disadvantages of the known processes and to allow conjugated diene dilithiation by a simple, smooth reaction in one step at short reaction times and relatively high reaction temperatures without process-technical difficulties. dilithium compounds in initiator solutions as well as high decomposition stability.

The invention is based on the need to develop - an improved process for obtaining highly concentrated dilithium-dienyl oligomer solutions - containing -; 2 to 6 monomer units per molecule, suitable as initiators for anionic polymerization of conjugated dienes and vinyl-substituted aro | matic compounds for telechelic polymers; meeting the above - mentioned requirements.

A process for the preparation of soluble organolithium polymerization initiators obtained by the reaction of lithium with conjugated dienes in the presence of polycyclic aromatic compounds and ethers, according to the invention, is to be reacted at temperatures; -30 to + 50 ° C, preferably from 10 to 30 ° C, for at least 1 hour, 0.5 to -1.5 gram gram of lithium per mole, β 4 to C 12 diene conjugated diene molecule in the presence of 5 to - 10 moles, a solvent consisting of a mixture of - 70 to 95% vol. - toluene or diethyl ether and 5 to 30% vol. - tetrahydrofuran, and in the presence of | 0.005 to 0.125 moles of polycyclic aromatic compound per lithium equivalent.

Polycyclic aromatic compounds are used as activators, of which naphthalene, anthracene or diphenyl are particularly preferred. Activator = ^{p p} OH Orujo adduct formation and report ^No. U is ^p otymeraci.! diene. It is expedient to use as little activator as possible, which is 0.005 to 0.125 moles per lithium equivalent in the process according to the invention. J

Preferably, the conjugated diene is 1,3-butyl. tadiene, isoprene or 2,3-dimethyl-1,3-butadiene.

Lithium can be in any form, for example, as a wire, chunks, or a fine powder, and can be equally good with lump lithium. i; In the preparation of soluble organolithium polymerization initiators - a mixture of toluene with tetrahydrofuran - or diethyl ether - is used as solvent. with tetrahydrofuran. The amount of solvent i is not a critical factor, however, 5 to 5 are used to achieve higher dilithium compound concentrations while providing solubility. 10 moles of solvent per mole of diene.

The reaction is generally feasible at temperatures.

I - - from -30 to +50 ° C, in view of other circumstances it is advantageous to carry out it at temperatures from +10 - to - +30 ° C. The reaction time should be at least 1 h, but may be extended to 3 h or more depending on other circumstances. I -;

The process according to the invention can be carried out under both positive pressure and atmospheric pressure. The advantage of the process according to claim 1 is that it makes it possible to carry out the dilithlation of conjugated dienes by a simple, smoothly running reaction in one step and at short reaction times and relatively high reaction temperatures without technological or difficulty. Doing so. - achieves high yields and high and high concentrations as well as high stability against! decomposition.

- Method - according to. . The invention - - can be - especially - advantageously carried out in particular as follows: - Into an inert atmosphere - an activator, lithium 3 and a cleaned and dried solvent mixture are introduced. Conjugated diene is added continuously to the reaction mixture over a period of up to 2 hours at normal pressure. The conjugated dienes, which are liquid at normal pressure and at room temperature, are added in the form of a mixture with solvents, butadiene is added as a gas, or in liquid form. The reaction temperature is preferably 20-25 ° C. After completion of the reaction, the unreacted lithium used in the next preparation was filtered off. ‘I

The resulting dilithium-dienyloligomers contain up to 6 nomomeric units per molecule and are fully soluble in the solvent mixture. The lithium content is 80 to 90% by weight, based on the lithium metal used, of which 90 to 95% by weight is in the form of a polymeric active bond.

The solutions have a concentration of from 1.6 to 2.6 lithium granatome per liter and can be stored for 2 to 4 weeks without loss of initiation activity. if stored at temperatures below + 5 ° C and under an inert atmosphere. | _}, And the invention can therefore be obtained by the process of replacing jednostupňoI concentrated stable solutions! organodilithium compounds of lithium and 1,3-dienes, even having a higher initiator activity.

The invention is also characterized in that dilithium dienyl oligomers can be prepared from readily accessible and relatively cheaper starting materials using molar amounts of lithium in lump form and lower amounts of lithium in lump form in lower amounts of activator as well as a shorter reaction time. | a relatively higher temperature while achieving a good yield.

The invention is further illustrated by the following examples.

Example 1

I Into a flask equipped with a stirrer and thermometer

I and 6.3 g of lithium in 7.68 g of naphthalene and 240 ml of toluene as well as 60 ml of tetrahydrofuran were introduced into the argon purging funnel. A solution of 40.8 g of isoprene, 120 ml of toluene and 30 ml of tetrahydrofuran was added dropwise from the dropping funnel over 2 hours. The temperature was maintained at 4-25 ° C. The reaction immediately began. After completion of the reaction, unreacted lithium was filtered off.

The resulting solution had a lithium concentration of 1.8 equivalents per liter. This corresponds to a lithium conversion of 90%. The activity (content of lithium bound to carbon) was 96%.

Example 2

Example 1 was repeated except that toluene / tetrahydrofuran was used instead; a mixture of diethyl ether with tetrahydrofuran having 10% by volume tetrahydrofuran. The lithium conversion was 80%, the lithium concentration in the solution was 1.45 equivalents per liter, and the initiator activity was 95.4%.

Example 3

The reaction flask of Example 1 was charged with 9.6 g of naphthalene, 4.2 g of lithium and a mixture of 150 ml of toluene with 50 ml of tetrahydrofuran. 40.5 g of butadiene gas were introduced with stirring at 20 ° C over 2 hours. After the addition of butadiene was complete, the reaction mixture was stirred for a further 1 hour, after which the unreacted lithium was filtered off. The lithium conversion was 85%. The solution showed a lithium concentration of 2.7 equivalents per liter and an activity of 96%.

Example 4

To the reaction flask of Example 1 was also charged 1.57 g of lithium in pieces, 1.92 g of naphthalene, ml of toluene and 15 ml of tetrahydrofuran. During | A solution of 21.6 g of 2,3-dimethyl-1,3-butadiene in 30 ml of toluene and 7.5 ml of tetrahydrofuran was added at 25 ° C for 1.5 h. After the addition of 2,3-dimethyl-

The 1,3-butadiene was stirred for a further 30 min and then the solution was filtered. At 80% lithium conversion, the lithium concentration was 1.6 equivalents per liter and the activity was 94%.

Claims (3)

SUBJECT OF THE INVENTION A process for the preparation of soluble organolithium polymerization initiators obtained by the reaction of lithium with conjugated dienes in the presence of polycyclic aromatic compounds and ethers, characterized in that it is reacted at temperatures from -30 to 30 ° C. 4-50 ° C, preferably from 10 to 30 ° C, for at least 1 hour, 0.5 to 1.5 grams of lithium per mole of conjugated diene of 4 to 12 carbon atoms per molecule in the presence of 5 to 10 moles of solvent, consisting of a mixture of 70 to 95% by volume of toluene or diethyl ether and 5 to 30% by volume of tetrahydrofuran and in the presence of 0.005 to 0.125 mol of polycyclic aromatic compound per lithium equivalent. 2. A process according to claim 1, wherein the polycyclic aromatic compound is naphthalene, anthracene or diphenyl. 3. A process according to claim 1 wherein the conjugated diene is 1,3-butadiene, isoprene or 2,3-dimethyl-1,3-butadiene.