CS231465B1 - Processing of lithium stsrthers of polymerization - Google Patents

Description

The invention relates to a process for preparing lithium polyfunctional type polymerization initiators by reacting meta- or para-divinylbenzene with a monoalkyllithium compound, in particular secondary butyllithium, in a hydrocarbon solvent.

It is known that lithium-containing polyfunctional polymerization initiators are prepared by reacting ortho-, meta- or para-divinylbenzene with alkylmonolithium, especially butyllithium, in inert organic solvents.

Multifunctional soluble organoalkal metal initiators are suitable for the synthesis of star polymers and for the preparation of end-functional polymers with a functionality greater than 2. The reaction of divinylbenzene with the organoalkal metal compound must be carried out in a very dilute state. The polyfunctional alkali metal compounds which are formed are more or less strongly branched or crosslinked to each other and constitute a microgel. Partially or wholly intermolecularly crosslinked products may also be formed. Such macrogels are insoluble and are of limited use as initiators for anionic polymerization. Soluble microgel crosslinked products are obtained only when the concentration of divinylbenzene in the reaction mixture is less than 2.5% by weight, and even within this concentration range the solubility of initiators is a function of the molar ratio of divinylbenzene to monolithium compound of 0.5: 1 to 20: 1 (DOS 2,427,955).

The greater the molar ratio of divinylbenzene to the low molecular weight organoalkal metal compound, the lower the divinylbenzene concentration in the reaction mixture must be because the increasing molar ratio increases the number of alkali metal to hydrocarbon moieties in the reaction product molecule, its molecular weight, and its degree of crosslinking.

It is known from DOS 2,427,955 to prepare an initiator at molar ratios of divinylbenzene to an alkali metal compound of 0.66: 1 to 1: 1, which can be calculated from the examples given. This provides more or less branched or crosslinked products which are microgels or macrogels. Linear compounds cannot be obtained at these molar ratios.

Also, the reaction time is an essential factor in the preparation of soluble multifunctional lithium initiators from divinylbenzene. According to the journal Plaste und Kautschuk 26/1979/5, pp. 263-264 and the patent Ja 80 06 652, short reaction times, i.e. rapid dosing of divinylbenzene, lead to gel solutions, i.e. also to crosslinked and polymeric products.

In the known process, the molar ratio of divinylbenzene to monoalkalometallic compound is 0.5 to 1 lower limit. The upper limit is determined by the concentration of divinylbenzene in the reaction mixture. Above a certain ratio, partial or complete intermolecular cross-linking occurs at a certain concentration to form insoluble macrogels. For example, the upper limit of the molar ratio is for a 2.5% 2: 1a solution at a 1.25% 6.7: 1 solution.

The known process has the disadvantage that it is not suitable for the synthesis of initiators for the anionic polymerization of monomers into low molecular weight telechelic polymers.

The desired low divinylbenzene concentration results in the formation of low-concentration initiator solutions. For the synthesis of polyfunctional organoalkalometallic initiators, an excess of divinylbenzene to the monoalkalometallic compound is always required, whereby all initiators are more or less strongly crosslinked, which strongly limits their solubility in hydrocarbon solvents. The initiators have a relatively high molecular weight of, for example, 2,800, 265,000 and 320,000, so that they cannot be used for the synthesis of low molecular weight polymers.

These disadvantages are overcome by a process for preparing polyfunctional type polyfunctional polymerization initiators by reacting meta- or para-divinylbenzene with secondary butyllithium in a hydrocarbon solvent by treating a solution of butyllithium in a hydrocarbon solvent with a divinylbenzene solution at a molar ratio of divinylbenzene to butyllithium n; n + 1, wherein n is a number of 2 to 6, for 15 to 60 minutes at 268 to

The reaction is carried out in the presence of a tertiary amine and the molar ratio of lithium to tertiary amine is 1: 1 to 1: 1.5.

Benzene or toluene may preferably be used as the hydrocarbon solvent. The tertiary amine may preferably be triethylamine, dimethylaniline or a mixture thereof. The concentration of divinyllbenzene is not very important for the process according to the invention. Soluble polyfunctional organolithium compounds are obtained at both low and high concentrations. The number of lithium atoms in the polyfunctional organolithium compounds is determined by the molar ratio of divinylbenzene to alkyl lithium and corresponds to the value of n + 1. The initiators of the invention are linear, non-crosslinked low molecular weight organolithium compounds.

Compared to the prior art, it is surprising that by the process according to the invention polyfunctional, low molecular weight, linear and non-crosslinked initiators can be obtained by reacting divinylbenzene with alkylmonolithium, without the disadvantages of known initiators.

Example 1

61.5 ml of 0.98 molar secondary butyllithium dissolved in benzene, 4 ml of triethylamine, 4 ml of dimethylaniline and 50 ml of benzene were introduced in a 500 ml sulfonation flask. To this mixture, a solution of 5.7 ml of meta-divinylbenzene in 20 ml of benzene from a dropping funnel was added at 30 ° C with stirring over 30 minutes. After the addition was complete, the mixture was stirred at this temperature for 2 hours. A red colored initiator solution was obtained and was functionalized with ethylene oxide to determine the degree of metalation.

After hydrolysis of the reaction product with 30 ml of water, the solution was centrifuged and the solvent was removed from the organic phase on a vacuum rotary evaporator at 323 K. The isolated divinylbenzene oligomer was determined by molecular weight osmosis in vapor phase in benzene. The hydroxyl group content was determined by acidometric titration. The product had an average molecular weight of 510 and a hydroxyl group content of 9.87%, corresponding to a functionality of 2.96.

Example 2

A mixture of 20 ml of a 1.4 molar solution of secondary butyllithium in benzene (28 mmol), 5 ml of triethylamine and 30 ml of benzene was added dropwise over 15 minutes at 278 DEG C. while stirring with 21 mmol of meta-divinylbenzene dissolved in 20 ml of benzene. The homogeneous reaction solution was further processed as in Example 1. The isolated product had an average molecular weight of 750 and a hydroxyl group content of 9.52%. From this, the functionality of 4.2 was calculated.

Example 3

Example 1 was repeated except that para-divinylbenzene was used instead of meta-divinylbenzene. The molecular weight of the hydroxylated product, determined by vapor phase osmometry, was 550, and a functionality of 3.1 was calculated from a hydroxyl group content of 9.58%.

Example 4

Example 1 was repeated except that the same volume of hexane was used instead of benzene, which did not affect the parameters of the resulting initiator.

Claims (3)

SUBJECT OF THE INVENTION Process for preparing lithium polyfunctional type polymerization initiators by reacting meta- or para-divinylbenzene with a secondary butyllithium in a hydrocarbon solvent, characterized in that a solution of butyllithium in a hydrocarbon solvent is treated with a divinylbenzene solution having a molar ratio of divinylbenzene to butyllithium in η: n + 1, wherein n is 2 to 6, for 15 to 60 minutes at 268 to 303 K, the reaction being carried out in the presence of a tertiary amine and the molar ratio of lithium to tertiary amine is 1: 1 to 1: 1.5. 2. The process according to claim 1, wherein the hydrocarbon solvent is benzene or toluene. . 3. A process according to claim 1 or 2, characterized in that triethylamine, dimethylaniline or a mixture thereof is used as the tertiary amine.