GB2124228A - Organo-lithium polymerization initiator - Google Patents

Abstract

A polymerization initiator is formed by metallization of a divinyl- benzene or mixture of divinyl- benzenes by reacting the divinyl- benzene(s) in an organic solvent or organic solvent mixture with a mono-, di- or trilithium organo compound. The resultant initiator can be used for forming a reactive polymer by anionic polymerization of a conjugated diene or anionic copolymerization of a conjugated diene with a vinyl aromatic monomer.

Description

SPECIFICATION Process for production of a polymerization initiator and polymerization process using the initiator The invention relates to a process for the production of polymerization initiators containing lithium, which will generally have an average functionality greater than 2 and are suitable for the production of telechelic homopolymers and copolymers of anionically polymerizable monomers, particularly of conjugated dienes and/or vinyl-substituted aromatic compounds.

Higher-functional alkali-metal-organo-initiators are required for the synthesis of polymers brandhed in star-shaped configuration and of terminally functional polymers with a functionality greater than 2 in anionic polymerization processes. As the so-called telechelic polymers themselves constitute low-molecular products with an average molecular weight of 1 000- 10000, the initiators used for their production must likewise have low molecular weights.

Preference is given to lithium initiators for polymerization reactions, as they offer various advantages by comparison with other alkali-metal organo-compounds, such as greater stability.

longer storability and suitably for use at comparatively high temperatures.

The majority of the bi-functional and multifunctional organic lithium compounds, however, are insoluble in hydrocarbons; it is only in higher polar solvents that they can be produced at all. If polymerization is carried out with initiator solutions of this kind, e.g. with an ether content, then secondary reaction, such as discontinuance or transfer of the chain or ether cleavage, are very liable to occur. This leads to a greater or smaller reduction of the content in active Li-C bonds, resulting in functionality losses, higher molecular weights for the polymers and less effective initiators.

It is known that polymerization initiators containing lithium and soluble in hydrocarbon can be produced by the reaction of divinylbenzene with monolithium alkylene, particularly butyllithium, in inert organic solvents. As a rule these metallization reactions are carried out with the use of m-divinylbenzene, as it does not tend to polymerize to the same extent as the other divinylbenzene isomers. Descriptions are thus given in "Plaste und Kautschuk" ("Plastics and Rubber") 26 (1979) 5, pp.263-264, Compt.

Rend. Hebd. Seances ("Weekly Reports of Meetings") of the Acad. Sci., Ser. C283 (1976) 4, pp. 123-125, U.S. Patent Specifications 3 725 368 and 3 862 251 and Ger. Unexamd.

Specn. 2 063 642 of how organolithium initiators can be produced by the reaction of mdivinylbenzene with alkyllithium compounds in a molar ratio of 1:2 in the presence or absence of tertiary amines. In all cases, however, only dilithium compounds are obtained. This method does not enable Li initiators of higher functionality to be produced.

According to Auslegungsschrift 2 003 384 and U.S. Patent Specifications 3 644 322 and 3 787 510 multifunctional Li initiators can be produced by the reaction of alkylithium compounds with divinylbenzene in a molar ratio of between 1:0.1 and 1:2 in the presence of solubilizing monomers, such as conjugated dienes or monovinyl aromatic substances, the molar ratio of alkyllithium compound to solubilizing monomer amounting to 1:2-1 These initiators suffer from their drawback that polymerizable monomers have to be added during the initiator synthesis in order to solubilize them, so that they themselves have high molecular weights and thus cannot be used for the synthesis of low-molecular polymers.

Furthermore, the functionality of the multi-lithium initiators can only be controlled through the number of vinyl groups of the polyvinyl aromatic substances or by means of a surplus of polyvinyl aromatic substance, involving the risk of crosslinking of the initiator, i.e. the danger of formation of gel.

According to Offenlegungsschrift 2 427 955 the reaction of divinylbenzene with the organoalkali metal compound must be carried out with a high degree of dilution. The resulting polyfunctional organo-alkali metal compounds are more or less considerably branched or crosslinked in themselves and constitute micro-gel.

Products of which the cross-linking or partly or completely inter-molecular may also occur.

Macrogels of this kind are insoluble and only of limited suitability for use as initiators for anionic polymerization.

Soluble products cross-linked in such a way as to form micro-gel are only obtainable, according to Offenlegungsschrift 2 427 955, if the concentration of the divinylbenzene in the reaction mixture is below 2.5% by weight, and even in this concentration range the solubility of the initiators is said to be a function of the molar ratio of the divinylbenzene to the monolithium compound, which should amount to 0.5-20:1.

The greater the molar ratio of divinylbenzene to organo-alkali metal compound of lower molecular weight, the lower must be the concentration of divinylbenzene in the reaction mixture, since an increase in the molar ratio involves an increased number of bonds between alkali metal and carbon per molecule of reaction products and an increase in the molecular weight and the degree of crosslinking of this latter.

Consequently, a molar ratio of divinylbenzene to mono-alkali metal compound of 0.5:1 is the lower limit. The upper limit is determined by the concentration of divinylbezene in the reaction mixture. Above a certain maximum ratio a certain concentration will be accompanied by partly or completely inter-molecular cross-linking, with the formation of insoluble macro-gels. With a 2.5% strength solution and a 1.25%-strength solution, for example, the upper limit of the molar ratio is about 2:1 and 6.7:1 respectively.

The process according to the prior art suffers from the following disadvantages, making it appear unsuitable as a means of synthetising initiators for the anionic polymerization of monomers to low-molecular telechelic polymers: - Owing to the low divinylbenzene concentration required the initiator solutions are likewise only of low concentration.

-The synthesis of the poly-functional organo alkali metal initiators invariably necessitates a surplus of divinylbenzene of the mono alkali metal compound, as a result of which all the initiators undergo more or less considerable cross-linking, whereby their solubility in hydrocarbon solvents is greatly reduced.

- The initiators themselves have relatively high molecular weights (e.g. 2800,265000 and 320000), so that they cannot be used for the synthesis of low-molecular polymers.

From Offenlegungsschrift 2 408 696 it is known that organo-trilithium polymerization initiators can be produced by the reaction of a divinyl aromatic compound, such as di-isopropenyl benzene or divinylbenzene, with an organomonolithium compound, such as sec.-butyl lithium, accompanied by the formation of a monoadduct and subsequent reaction of this latter, which still contains a free vinyl group, with an organo-dilithium compound, accompanied by the formation of the organo-trilithium compound. The synthesis process requires low temperature, particularly between 243 and 2730K. For the performance of the 2nd reaction stage (reaction of the mono-adduct with the organic-dilithium compound) tertiary amines are to be added, the molar ratio of amins to C-Li being 0.5-4:1.

As is known from Offenlegungsschrift 2 427 955 and Offenlegungsschrift 2 521 200, the reaction of divinylbenzene with alkyl lithium compounds, if carried out with molar ratios in which free vinyl groups are present, is accompanied by the formation of cross-linked products of the nature of micro-gel or macro-gel.

In the process covered by Offenlegungsschrift 2 408 696, therefore, it must be expected even in the first reaction stage that cross-linked reaction products will occur if divinylbenzene is used. With the use of di-iso-propenyl benzene there is no risk of cross-linking, as this is far less reactive than divinylbenzene and has a lower "ceiling temperature".

Di-iso-propenyl benzene, however, cannot be used on an industrial scale, owing to the expense involved in its synthesis.

The process to which Offenlegungsschrift 2 408 696 relates suffers from the further drawback that only trilithium compounds can be produced and that their synthesis involves a number of reaction stages. It is true that degrees of functionality between 2 and 3 are obtainable by the admixture of known dilithium compounds.

Initiators and polymers with a functionality of over 3 are not producible. Polymers of this kind, however, are necessary if cross-linked products with a high network density and good physicomechanical properties are to be obtained.

The purpose of the invention is to produce nonbranched multi-functional organo-lithium compounds of low molecular weight from readily obtainable raw materials which enable reactive polymers and block copolymers of low to medium molecular weight to be synthetized, in which process the polymers, after reaction with suitable electrophilic reagents, bear terminally functional groups and have a high degree of functionality and a narrow molecular weight distribution. The disadvantages of the known processes are thereby eliminated or minimized.

The purpose of the invention is to develop a process for the production of multi-functional polymerization initiators suitable for the anionic polymerization of conjugated dienes and the copolymerization of the said dienes with vinylaromatic monomers to form reactive polymers, in a manner which satisfies the conditions previously mentioned.

According to one aspect of the invention there is provided a process for the production of polymerization initiator by metallization of a divinylbenzenes, such initiator being capable of forming a reactive polymer by the anionic polymerization of a conjugated diene or vinyl aromatic monomer or anionic copolymerization of a conjugated diene with a vinyl aromatic monomer, the initiator-producing process comprising reacting in an organic solvent or organic solvent mixture a divinylbenzene or a mixture of divinylbenzenes with a mono-, di- or trilithium organo compound. Usually the lithium organo compound is a compound of lithium with a saturated or unsaturated aliphatic radical.

Where as divinylbenzene reactant there is used substantially pure 0-, m- or p- divinylbenzene or a mixture of two or more thereof, it is desirable to maintain a molar ratio of n:n+ 1 of said divinylbenzene compound of lithium organo compound wherein n is equal to or greater than 2 for a monolithium organo compound and a molar ratio of 1:2-10 for a dilithium or trilithium organo compound. Where as divinylbenzene reactant there is used an industrial divinylbenzene mixture, it is desirable to maintain a molar ratio of 1-2:1-10 of the vinyl groups in the industial divinylbenzene mixture to the lithium organo compound.

Preferably the reaction is carried out at 2683030K and preferably for a period of 15 to 60 minutes.

A tertiary amine, for instance triethylamine or dimethylamine, or a mixture of tertiary amines, may be present in order to increase the reactivity of the lithium organo compound, the molar ratio of lithium to the tertiary amine(s) being preferably 1:1-1.5.

Usually as solvent there is employed a hydrocarbon or hydrocarbon/ether mixture.

Aliphatic or aromatic hydrocarbons may be used, preference being given to aromatic hydrocarbons, such as benzene or toluene. Aliphatic or cycloaliphalic ethers, such as diethyl ether, methyl tert butyl ether or tetrahydrofuran, constitute preferred ether solvents.

In the reaction of 0-, m- or p-divinylbenzene or mixtures thereof with a monolithium organo compound, especially with an alkyl monolithium compound, preferably with n-, sec.- or iso-butyl lithium, the molar ratio of divinyl benzene to alkyllithium as indicated above amounts to n:n+1, n being a number greater than or equal to 2. The divinylbenzene concentration is not a decisive magnitude. Soluble polyfunctional lithium organo compounds are obtained both with low and with high divinylbenzene concentrations. The proportion of divinylbenzene isomers adopted when mixtures thereof are used is likewise not a decisive factor, but it is of advantage to employ mixtures of the kind which can be isolated from the industrial divinylbenzene mixture after the benzene alkylation.

The initiators produced by the process of the invention are linear non-cross-linked lithium organo compounds of low molecular weight. The number of lithium atoms per molecule of initiator is determined by the molar ratio of divinylbenzene to lithium organo compound, e.g. akyllithium compound and corresponds to the numerical value n+1. The functionality of these initiators can thus be controlled as required.

In the reaction of the lithium organo compound, e.g. a monolithium organo compound, with an industrial divinylbenzene mixture, which usually consists of (a) 1070% by weight of divinylbenzene(s); (b) 8030% by weight of ethyl styrene, and (c) 100% by weight of diethylbenzene, the molar ratio of vinyl groups in the industrial divinylbenzene (consisting of divinyl benzene plus ethyl styrene) to lithium organo compound, e.g.

alkyllithium, compound is preferably equal to 1.1-2:1. Here again the divinyl benzene concentration is not decisive. Soluble polyfunctional lithium or organo compounds of low molecular weight are obtained in any event, both with a low and with a high concentration of divinylbenzene.

The degree of metallization of the initiators produced by the process of the invention usually between 2 and 4.5, depending on the molar ratio of the vinyl groups to the lithium organo compound.

It is of advantage to use divinyl benzene mixture of the typre resulting from benzene alkylation and containing approximately 5070% by weight of divinylbenzene, 4020% by weight of ethylstyrene, and approximately 10% by weight of diethylbenzene.

In the reaction of the di- or trilithium organo compound with divinylbenzene in a hydrocarbon solvent, an ether or a mixture of hydrocarbon and ether, the molar ratio of the vinyl group in divinylbenzene or industrial divinylbenzene to the di- or trilithium compound, is generally 1:1-10.

Examples of organo dilithium compounds usable in the process are dilithium adducts of conjugated dienes, such as butadiene or isoprene, or dilithium alkanes, such as dilithium butane. An example of a suitable trilithium organo compound is the product of the reaction of divinylbenzene and sec. butyllithium in a molar ratio of 2:3.

The divinylbenzene can be used in the form of a pure o-, m- or p-isomer or mixtures of two or more thereof, producing either pure tetra- or hexalithium compounds or mixtures of tetra- or hexalithium compound and di- or trilithium compound, according to the metallization agent adopted (di- or trilithium compound) and the molar ratio of the vinyl groups to the said metallization means. Substantially pure lithium initiators of higher functionality are obtainable when the molar ratio of the vinyl groups to the metallizer is 1:1.

In addition to the pure divinyl benzene isomers and their mixture, however, the aforementioned industrial divinyl benzene mixtures can be advantageously employed for the production of the lithium organo polymerization initiators of higher functionality. If the same molar ratios of the vinyl groups to the metallization agent are retained, the process then provides mixtures of tetra- and dilithium compounds or mixture of hexa- and trilithium compounds. Initiator mixtures of this kind are of value in the production of polymers functional in the terminal state, since in cross-linking reactions the polymer chains of lower functionality act as chain-lengthening agents, the chemical structure of the polymer chain remaining the same.

The initiators according to the invention usually have a molecular weight of less than 500 and are thus particularly suitable for the synthesis of lowmolecular polymers. The initiator molecules of higher functionality are normally insoluble in the reaction medium. They can thus be isolated by known separating processes, such as filtering or centrifuging. They may nevertheless also be used for further reactions or converted by the addition of polymerizable monomers into a soluble form.

According to another aspect of the invention there is provided a process for forming a reactive polymer by the anionic polymerization of a conjugated diene vinyl aromatic monomer or anionic copolymerization of a conjugated diene with a vinyl aromatic monomer using the polymerization initiator defined by the first aspect of the invention.

The monomers capable of polymerization in the presence of these initiators are conjugated dienes, such as butadiene- (1,3) or isoprene, as well as vinyl-substituted aromatic compounds, such as styrene, alphamethyl styrene or divinyl benzene. The synthesis of copolymers can also be effected, however, with any of the other anionically polymerizable monomers as comonomers.

The polymerization may be carried out under the conditions known in connection with anonioc solution polymerizations with alkali metal organic initiators. Among suitable reaction media are aliphatic, cycloaliphatic and aromatic hydrocarbons, such as n-hexane, n-heptane, benzine fractions, cyclohexane, benzene or toluene. The polymerization is usually effected at temperatures of 1 98-4230K, preferably at 273-3230K, and at atmospheric pressure or above pressure. The reaction time is usually between 1 and 3 hours.

The quantity of initiator to be used is determined by the molecular weight desired, as the polymerization is stoichiometric. The heterogeneous initiators are converted by polymerizable monomers into a soluble form, so that the polymer solution becomes homogeneous in the course of the polymerization. Surprisingly enough, this does not lead to any wide distribution of molecular weights. The nonuniformity of the polymers, MW/Mn, averages 1.1 to 1.4.

The active chain ends of the resulting reactive polymers can be converted in the known manner with electrophillic reagents forming terminal groups, such as carbon dioxide, alkylene oxides, epichlorohydrin or gamma-butyrolactone, so that telechelic polymers can be produced in a highly advantageous manner.

During the polymerization reaction no subsidiary reactions occur, so that after the functionalization of the reactive polymers telechelic polymers of high functionality are obtained. The functionality of the polymers corresponds to that of the initiator. These polymers can be hardened in a simple manner, by means of bi-functional cross-linking agents.

The polymerization process to which the invention relates to characterized by the elimination or reduction of drawbacks inherent in methods known, such as inaccessibility of lowmolecular lithium initiators of higher functionality, limited effectiveness of the initiators, limited adjustability of molecular weight, wide distribution of molecular weights and low degrees of functionality in the polymer products.

The polymers obtained are of the stellate type and have a lower viscosity then the linear kind, with resulting improved workability.

The examples given are intended to illustrate the invention without in any way limiting its scope.

Examples Example 1 61.5 ml of 0.98 molar sec. butyllithium solution in benzene, 4 ml of triethylamine, 4 ml of dimethylaniline and 50 ml of benzene are provided in a 500-ml sulphonation flask. By means of a dropping funnel this mixture is treated with a solution of 5.7 ml of p-divinylbenzene (DVB) in 20 ml of benzene within 30 minutes, while stirring and at 298"K. After the introduction of the DBV has been completed the mixture is stirred for a further 2 hours at 2980 K. This results in a homogeneous dark red initiator solution which is functionalized by reaction with ethylene oxide in order to determine the degree of metallization.

After the hydrolysis of the reaction product with 30 ml of water the solution is centrifuged and the solvent removed form the organic phase in a vacuum rotary evaporator at 323 OK. The molecular weight of the isolated DVB oligomer is determined by vapour pressure osmosis in benzene and its hydroxyl content by acidimetric titration. The product has an average molecular weight of 550 and a hydroxyl content of 9.58%, corresponding to a functionality of 3.1.

A solution of 30 mmol of this trilithium initiator is treated with 600 ml of benzene in an argo atmosphere, 90 g of 1.3-butadiene then being added to the homogeneous solution within 2 hours. The polymerization temperature amounts to 2980K. After the completed polymerization the mixture is functionalized by reacting at 2780K with 7.9 g of ethlyene oxide and hydrolysed with water. The isolated polymer has an average molecular weight of 4100 (theoretically 3000) determined by vapour pressure osmosis and a hydroxyl content of 1.67% by weight, showing the functionality to be 3.04.

The proportion of 1 ,4-polybutadiene amounts to 57% (mol), while the 1,2-polybutadiene content is 34% (mol) and the divinylbenzene content 9% (mol).

Example 2 A solution of 21 mmol of m-DVB in 20 ml of benzene is added at 2780K, while stirring and within 1 5 minutes, to a mixture of 20 ml of 1.4 molar benzenic sec. butyl lithium solution (28 mmol), 5 ml of triethylamine and 30 ml of benzene. The mixture is then stirred for a further 2 hours at 2780K. The homogeneous reaction solution is worked up as in Example 1.

The isolated product has an average molecular weight Mn of 750 and a hydroxyl content of 9.52%. The degree of functionality calculated therefrom is 4.2.

1 4 mmol of this tetralithium initiator and 400 ml of toluene are provided in an argon atmosphere in a sulphonating flask. 56 g of 1,3butadiene is added at 3080K to this solution within 1.5 hours. After the butadiene has been added the mixture is stirred for a further 0.5 hour, after which the polymerization with 4.9 g of ethylene oxide is terminated and then hydrolysed with water.

This process provides a 100% yield of a liquid polybutadiene with an average molecular weight of 3900 and a microstructure of 57% (mol) of 1,4- and 39% (mol) of 1,2-units and a divinylbenzene content of 4% (mol). The molecular weight calculated from the ratio of monomer to initiator amounts to 4000.

The hydroxyl content calculated by acidimetric titration amounts to 1.726% by weight, corresponding to a functionality of 3.96.

Example 3 The starting mixture in a 500-ml sulphonating flask consists of 61.5 ml of a 0.98 molar sec.

butyllithium solution in benzene, 4 ml of triethylemaine, 4 ml of dimethylaniline and 50 ml of benzene. A solution of 20 mmol of a m-/pdivinylbenzene (DVB) mixture in a 20 ml of benzene is added to the foregoing starting mixture from a dropping funnel within 30 minutes and while stirring. After the addition of the DVB the mixture is stirred for a further 9 hours at 2900 K. This results in a homogeneous dark red initiator solution which is functionalized by reacting with ethylene oxide in order to determine the degree of metallization. After the hydrolysis of the reaction product with 30 ml of water the solution is centrifuged and the solvent removed from the organic phase in a rotary vacuum evaporator at 3230K.The molecular weight of the isolated DVB oligomer is determined by vapour pressure osmosis in benzene and the hydroxyl content by acidimetric titration. The product has an average molecular weight Mn of 760 and a hydroxyl content of 6.75%; corresponding to a functionality of 3.02.

72 g of 1,3-butadiene is polymerized within 2 hours at 2980K by a benzenic solution of 1 6 mmol of this trilithium compound dissolved in 400 ml of benzene. The resultant reactive polymer is then converted with 4.22 g of ethylene oxide and the result gel hydrolysed with water. A 100% yield of hydroxyl-terminated polybutadiene is obtained, with an average molecular weight of 4600 (theoretical molecular weight 4500) and an OH content of 1.085% by weight, indicating a functionality of 2.94. The polymer has a microstructure of 61% (mol) of 1,4 and 29% (mol) of 1,2 polybutadiene units. The non-uniformity U=MW/Mn amounts to 1.15.

Example 4 In a 750-ml sulphonating flask equipped with stirrer, thermometer, dropping funnel and argon supply the starting mixture provided is 40 mmol sec. butyllithium in 80 ml of benzene and 6 ml of triethylamine. 7.03 g of an industrial divinylbenzene mixture consisting of 57.2 by weight of divinylbenzene, 33% by weight of ethylstyrene and 9.8% by weight of diethylbenzene, dissolved in 40 ml of benzene, is added to the aforementioned starting mixture from a dropping funnel, within 1 5 minutes, at 2780K and while stirring. The mixture is stirred for a further 2 hours at 2780K. This leads to a clear solution with a dark red colour.

The latter is functionalized by reacting with 44 mmol of ethylene oxide in order to determine the degree of metallization. After hydrolysis with water, separation of the aqueous phase and removal of the solvent in a rotary vacuum evaporator, the functionalized intiator is examined analytically.

It is found to have an average molecular weight, determined by vapour pressure osmosis, of 920, with a hydroxyl content of 7.8%, from which the functionality calculated amounts to 4.22.

125 ml of this initiator solution and 300 ml of benzene are provided in an argon atmosphere in a sulphonating flask. 40 g of butadiene is added to this solution within 1 hour. After the completion of the reaction the mixture is stirred for a further 0.5 hours, after which the polymerization is interrupted with 44 mmol of ethylene oxide. The mixture is then hydrolysed with 50 ml of water, the aqueous phase separated and the solvent removed in a rotary vacuum evaporator. This process provides a 10% yield of a liquid polybutadiene with an average molecular weight of 4900 and a microstructure of 50% (mol) of 1,4 and 32% (mol) of 1,2 units and a divinylbenzene content of 18% (mol).

The hydroxyl content determined by acidimetric titration amounts to 1.42% by weight, corresponding to a functionality of 4.1.

Example 5 7.03 g of the industrial divinylbenzene mixture of Example 4 in 40 ml of toluene is added to drops to 63 mmol of iso-butyllithium dissolved in 100 ml of toluene.

The reaction time amounts to 30 minutes, and the temperature is 2980 K. After the completion of the reaction the mixture is converted with 76 mmol of ethylene oxide and processed as in Example 4. The molar ratio of the vinyl groups to the butyllithium is 1.25:1. The average molecular weight of the functionalized initiator is 450 and the hydroxyl content 8.5% by weight. This indicates a functionality of 2.25.

A solution of this initiator in 140 ml of toluene is treated, in an argon atmosphere, with 400 ml of toluene, 63 g of isoprene being added to the homogeneous solution within 1 hour. The polymerization temperature is 273"K. After the completion of the polymerization the mixture is functionalized by reaction with 76 mmol of ethylene oxide and processed as in Example 4.

The isolated polyisoprene has an average molecular weight of 2600 and a hydroxyl content of 1.41% by weight. This indicates a functionality of 2.1 5. The theoretical molecular weight is 2700.

Example 6 Example 4 is repeated, with the difference that in this case use is made of 80 mmol of n-butyllithium and 15.42 g of an industrial divinylbenzene mixture containing 51.8% by weight of divinylbenzene, 30.7% by weight of ethylstyrene and 17.5% by weight of diethylbenzene.

The functionalized initiator is found by vapour pressure osmosis to have an average molecular weight of 850. The hydroxyl content is 8.84% by weight and the functionality 4.42.

By means of this initiator, dissolved in 750 ml of benzene, 60 g of butadiene and 40 g of styrene are polymerized in succession at 2320K within 2 hours. The mixture is then functionalized by reaction with 88 mmol of ethylene oxide and processed in the usual manner.

The resulting block co-polymer consists of 74.5% (mol) of butadiene and 25.5% (mol) of styrene. The molecular weight is 5400 and the functionality 4.3, corresponding to a hydroxyl content of 1.35% by weight.

Example 7 In a 750-ml sulphonating flask, equipped with a stirrer, thermometer, dropping funnel and argon supply, 400 ml of a 1-molar solution of a dilithium adduct of butadiene, containing 2 monomer units per molecule, is provided in a toluene tetrahydroduran mixture (volumetric ratio 85:15)31.6 g (0.2 moi) of m-divinylbenzene, dissolved in 100 ml of toluene, is added from a dropping funnel within 30 minutes at 2680K. The mixture is then stirred for a further 1 hour. During the addition of the solution in drops and the stirring process, the tetralithium compund is precipitated from the solution. The suspension is functionalized by reaction with 1 mol of ethylene oxide, while stirring, in order to determine the degree of metallization.After hydrolysis with water, separation of the aqueous phase and removal of the solvent in a rotary vacuum evaporator, the functionalized initiator is examined analytically.

It is found to have a molecular weight of 480, determined by vapour pressure osmosis, and a hydroxyl content of 13.46%, from which the functionality is calculated at 3.8.

Example 8 25.2 mol of an industrial divinylbenzene mixture containing 30% (mol) of ethylstyrene and 60% (mol) of divinylbenzene, dissolved in 1 50 ml of benzene, is added in drops, within 60 minutes and at 3030K, to a solution of 0.24 mol of dilithiumbutane in 300 ml of methyl-tert. butyl ester. The molar ratio of dilithiumbutane to the vinyl groups in the industrial DVB mixture is 1:1.

The at first clear and colourless solution precipitates a yellowish deposit.

The initiator is hydroxylated and processed in the same manner as in Example 7.

The average molecular weight of the functionalized initiator is 340 and the hydroxyl content 16.5%. This corresponds to an average functionality of 3.3.

Example 9 Example 7 is repeated, except that in place of the dilithium compound the starting mixture in the flask consists of 0.4 mol of a trilithium adduct of m-divinylbenzene and sec.-butyllithium in 200 ml of benzene, 0.2 mol of p-divinylbenzene being added in drops at 2780K. The functionalized initiator has an average molecular weight of 830, a hydroxyl content of 11.8% and a functionality of 5.75.

Example 10 38.5 mmol of a tetralithium initiator, obtained from 77 mmol of a dilithiumoligoisoprene, containing an average of 2 isoprene units per molecule, and 38.5 mmol of m-divinylbenzene, suspended in 1.5 litres of a toluene and tetrahydrofuran mixture (volumetric ratio 95:5), are provided as the starting mixture is a secured 2.5litre sulphonating flask, 1 55 g of butadiene-(1,3) being added at 2730C. The polymer solution becomes homogeneous after the addition of 1/3 of the butadiene. 185 mmol of ethylene oxide is now added, while stirring, the solution thereby immediately solidifying to form a firm white gel.

The latter is destroyed by hydrolysis with 50 ml of water, the solution thereby again becoming thinly liquid. The aqueous phase is centrifuged off from the toluenic solution together with the LiOH which has formed. 1.55 g of di-tert.-butylcresol is added to the toluenic solution, after which the solvent is removed in a rotary vacuum evaporator.

This process yields a thinly liquid polymer with an average molecular weight Mn of 4400 (theoretical molecular weght: 4380) and a functionality, F, of 3.8. The microstructure, determined by NMR spectroscopy, was found to be 90% 1,2- and 10% 1 ,4-polybutadiene.

Example 11 A suspension of 30 mmol of hexalithium initiator which was obtained by the reaction of 30 mmol of an m/p-divinylbenzene mixture with 90 mmol of a trilithium compound, which is the product of the reaction of sec.butyllithium with pdivinylbenzene in a molar ratio of 3:2, is treated, in an argon atmosphere, with 600 ml of benzene, after which 135 g of butadiene-(1,3) is added within 2 hours. The polymerization temperature is 298by. After the completion of the polymerization the mixture is functionalized by reaction with 21 6 mmol of ethylene oxide, at 2780K and hydrolysed with water. After the removal of the solvent the isolated polybutadiene is found by vapour pressure osmosis to have an average molecular weight of 3700 (theoretical: 3715) and a hydroxyl content of 2.67% by weight, indicating a functionality of 5.8.The proportion of 1,4-polybutadiene amounts to 69% (mol) and the proportoin of 1,2-polybutadiene to 31%(mol).

Example 12 22 mmol of a hexalithium initiator produced from 20 mmol of m-divinylbenzene and 60 mmol of a trilithium compound obtained from sec.butyllithium and m-divinylbenzene in a molar ratio of 3:2, in benzene, and 600 ml of toluene are placed in a sulphonating flask in an argon atmosphere.

60 g of butadiene and 40 g of styrene are added to this suspension within 1.5 hours. After the addition of the styrene the mixture is stirred for a further 0.5 hour, the resultant reactive polymer then being functionalized by reaction with gaseous carbon dioxide. The carboxylate thus formed is converted with HC1 gas to the hexacarbonic acid. Surplus HC1 is neutralized with Na2CO3, and the alkali metal salts are filtered off. After the removal of the solvent the yield is 100%.

The resulting butadiene/styrene block copolymer has an average molecular weight Mn of 4200 and a functionality of 5.98.

Example 13 An initiator produced from 4 g of an industrial divinylbenzene mixture, which consists of 60.3% by weight of divinylbenzene (18 mmol), 30.3% by weight of ethylstyrene (9 mmol) and 9.4% by weight of diethylbenzene (2.9 mmol), and 75 mmol of dilithiumbutane, in 100 ml of methyl tert.

butyl ether, is treated with 500 ml of benzene, in an argon atmosphere and 210 g of butadiene (1,3) is added to the mixture within 2.5 hours at 2980K, while stirring. After the completion of the polymerization the mixture is cooled down to 2780K and 180 mmol of ethylene oxide added.

The white gel thus formed is hydrolysed with 50 ml of water, the aqueous solution removed and the solvent distilled out of the organic phase in a rotary vacuum evaporator. The resulting liquid polybutadiene has a molecular weight, M,, of 4050'(theoretical 4000) and a functionality of 2.47 (theoretical: 2.5). The proportoin of 1,2polybutadiene amounts to 45% (mol) and the proportoin of 1,4-poiybutadiene to 55% (mol).

Example 14 An initiator suspension obtained by the reaction of 40 mmol of m-divinylbenzene with 1 60 mmol of a trilithium compound, the latter being produced from sec.butyilithium and mdivinylbenzene, in a molar ratio of 3:2, in 200 ml of benzene, is treated with 500 ml of benzene, after which 240 g of butadiene is added within 2 hours. The polymerization temperature amounts to 2080 K. The solution of the resultant reactive polybutadiene is then treated with 0.57 mol of ethylene oxide at 2780C. The alcoholate forming in hydrolysed with 100 ml of water. The aqueous phase and the Li salts are centrifuged off.

After the removal of the solvent from the organic phase in a rotary vacuum evaporator a liquid polybutadiene is obtained with an average molecular weight of 2700 and a functionality of 3.93 (theoretical: 4.0). The polymer contains 65% (mol) 1,4-units and 35% (mol) 1,2-units.

Example 15 100 g of butadiene-(1,3), which is obtained from 4 g of an industrial divinylbenzene mixture containing 60.3% by weight of divinylbenzene (18 mmol), 30.3% by weight of ethylstyrene (9 mmol) and 9.4% by weight of diethylbenzene, and 54 mmol of the trilithium compound of Example 14, is polymerized in 400 ml of toluene within 2 hours and at 3230K. 35 g of styrene is then added within 1 hour. The mixture is then functionalized by reaction with 194 mmol of ethylene oxide and processed in Example 14.

The isolated butadiene styrene co-polymer has an average molecular weight of 3500 and an average functionality of 3.9 (theoretical 4.0). The molar composition amounts to 85% butadiene and 15% styrene. Yield: 100%.

Claims (24)

Claims

1. A process for the production of a polymerization initiator by metallization of a divinylbenzene or a mixture of divinylbenzenes, such initiator being capable of forming a reactive polymer by the anionic polymerization of a conjugated diene or vinyl aromatic monomer or anionic copolymerization of a conjugated diene with a vinyl aromatic monomer, the initiatorproducing process comprising reacting in an organic solvent or organic solvent mixture a divinylbenzene or a mixture of divinylbenzenes with a mono-, di- or trilithium organo compound.

2. A process according to Claim 1, wherein the lithium organo compound is a compound of lithium with a saturated or unsaturated aliphatic radical.

3. A process according to Claim 1 or Claim 2, wherein as divinylbenzene reactant there is used substantially pure o-, m- or p- divinylbenzene or a mixture of two or more thereof, a molar ratio of n:n+ 1 of said divinylbenzene compound to lithium organo compound wherein n is equal to or greater than 2 being maintained for a monolithium organo compound and a molar ratio of 1: 2-10 being maintained for a dilithium or trilithium organo compound.

4. A process according to Claim 1 or Claim 2, wherein as divinylbenzene reactant there is used an industrial divinylbenzene mixture, a molar ratio of 1-2:1-10 of the vinyl groups in the industrial divinylbenzene mixture to the lithium organo compound being maintained.

5. A process according to any preceding claim, wherein the reaction is carried out at 268 3030K.

6. A process according to any preceding claim, wherein the reaction is carried out for a period of 1 5 to 60 minutes.

7. A process according to any preceding claim, wherein the reaction is performed in the presence of at least one tert. amine.

8. A process according to Claim 7, wherein the molar ratio of lithium to the tertiary amine(s) is 1:1-1.5.

9. A process according to any preceding claim, wherein as solvent there is used a hydrocarbon or hydrocarbon/ether mixture.

10. A process according to Claim 4 or any claim appendant thereto, wherein the industrial divinylbenzene mixture comprises: (a) 1070% by weight of divinylbenzene(s); (b) 8030% by weight of styrene; (c) 100% by weight of diethylbenzene.

11. A process according to Claim 4 or any claim appendant thereto, wherein the molar ratio of the vinyl groups in the industrial divinyl mixture to the lithium organo compound is as follows:

1.1 to 2: for a monolithium organo compound, and 1 :1-lOfora dilithium trilithium organo compound.

1 2. A process according to any preceding claim, wherein an alkyllithium compound is used as monolithium organo compound.

13. A process according to Claim 12, wherein the alkyllithium compound is n-, sec.- or isobutyllithium.

14. A process according to any one of Claims 1 to 11, wherein as dilithium organo compound there is used a dilithium adduct of butadiene or isoprene, which adduct contains 1 to 7 diene units per molecule, or there is used dilithiumbutane.

1 5. A process according to any one of Claims 1 to 11, wherein as trilithium organo compound there is used a product of the reaction of divinylbenzene and sec. butyllithium in a molecular ratio of 2:3.

1 6. A process according to Claim 9 or any claim appendant thereto, wherein the hydrocarbon is chosen from benzene and toluene and/or the ether is chosen from diethyl ether, methyltert.butyl ether or tetrahydrofuran.

1 7. A process according to Claim 7 or any claim appendant thereto wherein the tert.

amine(s) is/are constituted by triethylamine or dimethylamine or a mixture thereof.

18. A process according to Claim 1, substantially as herein described and exemplified.

1 9. A polymerization initiator which has been obtained by the process claimed in any preceding claim.

20. A process for forming a reactive polymer by the anionic polymerization of a conjugated diene or vinyl aromatic monomer or anionic copolymerization of a conjugated diene with a vinyl aromatic monomer using the polymerization initiator defined by Claim 1 9.

21. A process according to Claim 20, wherein the polymerization is carried out at a temperature of 198 to 4230K.

22. A process according to Claim 21, wherein the temperature is 273 to 323 OK.

23. A process according to Claim 20, substantially as herein described and exemplified.

24. A reactive polymer which has been produced by the process claimed in any one of Claims 20 to 24.