GB2516233A

GB2516233A - Microstructure modification of polydienes using polar modifiers

Info

Publication number: GB2516233A
Application number: GB1312606.5A
Authority: GB
Inventors: Yulia Rogan; Simon Beal; Darren Rhodes
Original assignee: Thomas Swan and Co Ltd
Current assignee: Thomas Swan and Co Ltd
Priority date: 2013-07-15
Filing date: 2013-07-15
Publication date: 2015-01-21
Anticipated expiration: 2033-07-15
Also published as: GB2516233B; GB201312606D0

Abstract

A process for synthesis of a rubbery polymer comprises copolymerising a diene, such as butadiene or isoprene, in an organic solvent, such as hexane, at temperature 30-150oC is characterised by a catalyst comprising an organolithium initiator, such as n-butyl lithium, and one or more heterocyclic compounds, polar modifiers, containing two heteroatoms, one of which is nitrogen substituted with a tetrahydrofuran-2-ylmethyl group, such as 4-[(tetrahydro-2-furanyly) methyl] morpholine. The polar modifiers can be used to polymerise isoprene monomer into high 3,4-polyisoprene with an excellent polymerisation rate.

Description

Microstructure modification of polydienes using polar modiliers (application of tn-or tetra-dendate structurally constrained compounds based on heterocycles containing two heteroatoms) The present invention relates to the provision of alternative polar modifiers for modification of the structure, reaction and subsequent work up of the polymerisation of conjugated dienes so as to provide rubbery polymers, i.e. synthetic rubber; polymers having elastomeric properties.

General Background

It is important that polydienes which are used in many applications to have high vinyl contents.

For example, 3,4-polyisoprene can be used in tire tread compounds to improve tire perfonnance characteristics, such as traction, for example exemplified by such as wet braking and cold temperature braking. Polar modifiers arc commonly used in the preparation of synthetic polydiene rubbers which are prepared utilizing lithium catalyst systems in order to increase their vinyl content. Nigh vinyl content improves interaction between the polymers and the silica fillers refining rolling resistancc of a tire. Ethers and tertiary amines which act as Lewis bases are commonly used as modifiers. The skilled person in this technical field, for example providing polydienes (and copolymers thereof, particularly with styrene) makes use of a wide portfolio of polar modifiers so as to tailor the particular polymer structure resulting from a polymerisation reaction of a diene to particular requirements. Those requirements whilst including the exemplary characteristic of high vinyl content also includes other significant parameters such as randomness of eomonomer incorporation (such as styrene); eis -trans isomerism ratios of the vinyl content; rate of polymerisation (i.e. increase in molecular weight over time) by means of reaction temperature and ease of removal of polymerisation by-products and additives, such as the polar modifier.

Prior Art

Ethers and tertiary anlines which act as Lewis bases are commonly used as polar modifiers to obtain the above effects. For instance, U.S. 4,022,959 indicates that (hethyl ether, di-n-propyl ether, diisopropyl ether, di-n-butyl ether, tetrahydroftiran, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol diniethyl ether, trimethylaniine, triethylamine, N,N,N' ,N'-tetramethylethylenediamine, N-methyl morpholine, N-ethyl morpholine, and N-phenyl morpholine can be used as modifiers. U.S. Patent No. 4,696,986 describes the use of 1,2,3-trialkoxybenzenes and 1,2,4-trialkoxybenzencs as modifiers. The vinyl group content of polydienes prepared utilizing Lewis bases as modifiers depends upon the type and amount of Lewis base employed as well as the polymerization temperature utilized. For example, if a higher polymerization temperature is employed, a polymer with a lower vinyl group content is obtained (see A.W. Langer; A, Chem. Soc. Div. Polymer Chem. Reprints, 1966, vol. 7 (1), 132; A.F.Halasa, et.al. J. Pol. Sci: Pol. Chem Ed., 1981, vol 19, 1357). For this reason it is difficult to synthesize polymers having high vinyl contents at high polymerisation temperatures utilizing typical Lewis base modifiers. Higher temperatures generally promote a faster rate of polymerization. Accordingly, it is desirable to utilize moderately high temperatures in commercial polymerisations in order to maximize throughputs. US 5231153 descnbcs a process for the synthesis of a rubbery polymer which comprises homopolymerisation of isoprene and copolymerisation of styrene with isoprene or styrene with butadiene in an inert organic solvent at a temperature which is within the range of about 30°C to about 125°C in the presence of a catalyst system which is comprised of (a) an organolithium initiator and (b) an alkyl tetrahydrofurfuryl ether modifier, wherein the alkyl group in the alkyl tetrahydrofurfuryl ether contains from Ito 10 carbon atoms, producing polymers and copolymers with vinyl content up to 70% at a molar ratio of polar modifier to initiator 1 tol. CN 10184511 OA suggests using as a polar modifiers oxygen-conlaiinng heterocycles and nitrogen-containing heterocycles compounds to regulate microstructure of butadiene homopolymer and butadiene-styrene copolymcr, which has one saturated oxygen heterocycle alkyl and one nitrogen heterocycle alkyl, where the o-position C of the oxygen heterocycle is connected with the N through the methylene bridge and wherein N-containing cycle is 5-8 member ring. W02011/087841 discuss the use of 2,2-bis(2-tetrahydrofurvl)propane (DTHFP) as polar modifier as a mixture or isolated mesoD,L isomers pointing to a difference in behaviour of isolated isomers in microstructure modification. Current modifier is already in use in tyre production; however, its application has restrictions by solubility in water and as a result a poorer purification of the final product.

Other disclosures of polar modifiers in this technical field include; US5336739 which discloses Alkyl tetrahydrofurfuryl ethers as anionic polymerization modifier hi the synthesis of rubbery polymer; US5359016, which discloses a process for the synthesis of styrene-isoprene rubber; US5448003, which discloses synthesis of rubbery polymer using anionic polymerization modifier; US5470929, which discloses a process for synthesizing styrene-isoprene rubber; U55612436, which discloses Isoprene-butadiene diblock rubber; US6515087, which discloses synthesis of elastomers having low hysteresis; (JS8344063, which discloses monomodal coupled diene elastomer having a silanol thnctional group in the middle of the chain, its process of preparation and rubber composition comprising it; and US 2012-0108773 which discloses catalysts for polymerization of isoprcnc and preparations and uses thereof.

Problems addressed by the present invention An object of the present invention is to increase the portfolio of polar modifiers available, for the polymerisation of dienes, to the formulator of rubbery polymer products. The formulator when carrying out polymerisations of a diene to produce a rubbery polymer is required to tailor multiple parameters depending on the end product and its use, for example summer tyre rubber compound, winter tyre rubber compound, environmentally efficient tyre compound etc. The interplay of the parameters of randomness of comonorner incorporation (such as styrene); vinyl content; cis -trans isomerism ratios of the vinyl content; rate of polymerisation (i.e. increase in molecular weight over time) and ease of removal of polymerisation by-products and additives mean that there is not necessarily anyone best' ratio or combination of such factors since different end applications benefit fiom different combinations. A polar modifier providing alternative results is therefore inherently beneficial to the formulator.

Relevant attributes of the present invention are; the provision of a polar modifier giving rise to high vinyl content; the provision of a polar modifier giving rise to a high degree of randomness of styrene incorporation in styrene butadiene rubber; the provision of a polar modifier readily removable by water extraction at the polymerisation any provision of a polar modifier capable of operating at a higher reaction temperature and hence achieving rapid reaction.

Summary of the invention

The present invention in its various aspects is as set out in the appended claims.

It has been determined that compounds having the following structural formulae; as shown below and labelled A, B, C. D, B and F; can be used as polar modifiers in the synthesis of polydienes, wherein R = H, an alkyl group containing from 1 to 10 carbon atoms, an aryl group containing from 6 to 10 carbon atoms, or a divalent organic chain to form a dimer defined by structure F, R1 = an alkyl group containing from 1 to 10 carbon atoms or an aryl group containing from 6 to 10 carbon atoms and R2 is a bivalent saturated, saturated or unsaturated, hydrocarbon radical of from 1 to 10 carbon atoms or a bivalent aryl group containing from 6 to carbon atoms: R is preferable H or CH3, more preferably H. 3N

A B C D

E

F

The structures A to F being are termed collectively herein the 1-leterocycles and individually a Heterocycle. The preferred heterocycle is A. The polar modifiers of the present invention can be used in the production of rubbery polymers (also comnonly known as synthetic rubber) which are made by the polymerization of;l,3-butadiene, particularly as a copolvmer of styrene to provide styrene-butadiene rubbers (SBR); and isoprene (2-methyl-i,3-butadienc).

Tt has been unexpectedly discovered that heterocycle compounds A, B, C, D and F (particularly A), can be used as polar modifiers to modit anionic polymerizations of conjugated diene monomers to provide a new combination of features. These Heteroeycles of the present invention can be used to polymerize isoprene monomer into high 3,4-polyisoprenc at excellent polymerization rates. This is in contrast to convenfional polar modifiers such as tetramethylethylene diarnine and ethyltetrahydrofurfuryl ether which are typically used as polar modifiers to modifi such polymerizations. It has been unexpectedly discovered that various compounds, such as alkyl Ietrahydrothrfuiyl ethers, can be used to modit' anionic polymerizations of conjugated diene monomers. These Heterocycles of the present invention can be used to polymerize isoprene monomer into high 3,4-polyisoprene at high polymerization rates. These Heterocycles of the present invention can also be used to polymerise dienes to give a high vinyl content (i.e. 70% or more). These Heterocycles of the present invention can abo be used to give a high randonmess of styrcnc incorporation in styrcnc butadiene copolymem. These Heterocycles of the present invention can also be used to facilitate work up of the reaction mixture after polymerisatioii as, due to their water solubiliw, they are readily removed by washing with water (and therefore also potentially recoverable for the use in the reaction). This is in contrast to the conventional polar modifiers such as tetramethylethylene diamine which are typically used to modify such polymerizations and advantageous convert to tetrahydrofurfuryl ethers.

The process of producing polydienes of thc present invention requires an organo lithium initiator, preferably n-BuLi. The use of the lleteroeycles of the present invention can result in formation of high vinyl contents, these giving rise to beneficial tyre properties when used in that application.

The modifiers of this invention remain stable at 70°C, and even up to 100°C polymerization temperature and can lead to the formation of polymers having high vinyl contents at such temperatures. Accordingly, they can be used to promote the fonnation of high vinyl polymers at temperatures which are high enough to promote very fast polymerization rates.

The polymers which can be prepared utilizing the modifiers of the present invention are organolithium-initiated, vinyl group containing polymers of at least one diolefin monomer which are generally rubbery (elastomeric) polymers. The diolefin monomers utilized in the preparation of such polymers normally contain from 4 to 12 carbon atoms with those containing fiom 4 to S carbon atoms being more commonly utilized. The diolefin monomers used in such polymers are normally conjugated diolefins.

The conjugated diolefin monomers which are utilized in the synthesis of such polymers generally contain from 4 to 12 carbon atoms. Those containing from 4 to S carbon atoms are generally preferred for commercial purposes. For similar reasons, 1,3-butadiene and isoprene are the most commonly utilized conjugated diolefin monomers and are preferred. Some additional conjugated diolefin monomers that can be utilized include 2,3-dimethyl-1,3-butadiene, piperylene, 3-butyl-1,3-octadiene, 2-phenyl-1,3-butadiene, and the like, alone or in admixture.

Feed stocks which are comprised of one or more conjugated diolefrn monomers in admixture with other low molecular weight hydrocarbons can be utilized. Such admixtures, termed low concentration diene streams, are obtainable from a variety of refinery product streams, such as naptha-eraeking operations or can be intentionally blended compositions. Some typical

S

examples of low molecular weight hydrocarbons which can be admixed with diolefin monomers, such as 1,3-butadiene, in the polymenzafion feed include propane, propylene, isobutane, n-butane, 1-butene, isobutylene, trans-2-butene, cis-2-butene, vinylacetylene, cyclohexane, ethylene, propylene.

Copolymers of one or more diolefin monomers having high vinyl contents can also be prepared utilizing the modifiers of the present invention. For instance, copolymers of isoprene and butadiene having high vinyl contents can be synthesized.

Polydiene rubbers having high vinyl contents which are copolymers or terpolymers of diolefin monomers with one or more other ethylenically unsaturated monomers which are copolymerizable with diolefin monomers can also be prepared utilizing the [-leterocycles of the present invention. Some representative examples of ethylenically unsaturated monomers that can potentially be synthesized into such high vinyl polymers include ailcyl acrylates, such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate and the like; vinylidene monomers having one or more terminal CR2 -CU-groups; vinyl aromatics such as styrene, alpha.-methylstyrene, bromostyrene, chlorostyrcne, tluorostyrcnc and the like; .alpha.-olefins such as ethylene, propylene, 1-butene, and the like; vinyl halides, such as vinylbromide, chloroethane (vinylchloride), vinylfluoride, vinyliodide, 1,2-dibromoethene, 1,1 -dichloroethene vinylidene chloride), l,2-dichloroethene, and the like; vinyl esters, such as vinyl acetate; alpha.,.beta.-oleflnically unsaturated nitriles, such as acrylonitrile and methaerylonitrile; alpha.,.beta.-oleflnically unsaturated aniides, such as acrylamide, N-methyl acrylaniide, N,N-dimethylacrylamide, methaervlamide.

Polydiene rubbers which are copolymers of one or more diene monomers with one or more other ethylenically unsaturated monomers will normally contain from about 50 weight percent to about 99 weight percent diene monomers and from about 1 weight percent to about 50 weight percent of the other ethylenically unsaturated monomers in addition to the diene monomers. For example, copolymers of diene monomers with vinylaromatic monomers, such as styrene-butadiene rubber (SBR) which contain from 50 to 95 weight percent diene monomers and from to 50 weight percent vinylaroniatic monomers are useful in many applications.

Vinyl aromatic monomers are a class of ethylenically unsaturated monomers which are conventionally incorporated into polydienes. Such vinyl aromatic monomers are selected so as to be copolymerizable with the diolefin monomers being utilized. Generally, any vinyl aromatic monomer which is known to polymerize with organolithium initiators can be used. Such vinyl aromatic monomers typically contain from S to 20 carbon atoms. Usually the vinyl aromatic monomer will contain from S to 14 carbon atoms. The most widely used vinyl aromatic monomer is styrene. Some examples of vinyl aromatic monomers that can be utilized include styrene, I -vinylnaphthalene, 2-vinylnaphthalene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, most preferably styrene.

The relative amount of conjugated diene or dienes and monovinyl aromatic compound or compounds employed can vary over a wide range. In preparing rubbery polymers, the proportion of the conjugated diene versus the monovinyl-substituted aromatic compound should be sufficient so as to result in a substantially rubbery or elastomeric copolvmer product. There is no sharp step change as to the amount of conjugated diene versus monovinyl-substituted aromatic compound that confers rubbery or elastomeric properties on the resulting copolymer, though in general at least 50 parts by weight of conjugated diene are required on an exemplary basis. Thus, for a rubbery copolymer, as is preferred in accordance with this invention, the weight ratio of conjugatcd diene to monovinyl aromatic compound in the monomer charge would be in the range of about 50:50 to 95:5. Mixtures of conjugated dienes as well as mixtures of monovinyl-substituted aromatic compounds can be utilized.

In solution polymerizations which utilize the I-leterocycles of the present invention, there will normally be from 5 to 35 weight percent monomers in the polymerization medium. Such polymerization mediums comprise an organic solvent, monomers, an organolithium initiator, and the modifier. In most cases it will be preferred for the polymerization medium to contain from 10 to 30 weight percent monomers. It is generally more preferred for the polymerization medium to contain 20 to 25 weight percent monomers.

The amount of organolithium initiator utilized will be adapted to the monomers being polymerized and with the molecular weight that is desired for the polymer being synthesized.

However, typically 0.01 to 1 phm to (parts per 100 parts by weight of monomer) of an organolithium initiator is used, preferably 0.025 to 0.07 phm of the organolithium initiator.

The initiator may be selected depending upon the degree of branching and the degree of elasticity desired for the rubbery polymer, the nature of the monomer fcedstock. With regard to the feedstock employed as the source of conjugated diene, for example, the multifijnctional initiator types generally are preferred when a low concentration diene stream is at least a portion of the feedstock, since some components present in the unpurified low concentration diene stream may tend to react with carbon lithium bonds to deactivate initiator activity, thus necessitating the presence of sufficient lithium functionality hi the initiator so as to overcome such effects.

The amount of heterocycle, or heterocycles mixture of the present invention needed to be effective in polymerisations will vary with the vinyl content which is desired for the polymer being synthesized. For instance, polymers with only slightly increased vinyl contents can be prepared by utilizing as little as 0.1 moles of the modifier per mole of metal in the organometallic initiator being utilized. If polymers having very high vinyl conlents arc desired, then large quantities of the modifier can be used. This emphasises that the former later when choosing a polar modifier finds benefit from the use of alternative materials rather than simply seeking high levels of any specific property. In general terms, in choosing the level of hetcrocycle to be used thc former later will not be expect to employ more than about 40 moles of the Hcterocycle(s) pcr mole of metal in the organomctallic initiator system employed. In most cases from about 0.25 to about 15 moles of the Fleterocycle(s) will be employed per mole of metal in the organometallic initiator system utilized. Preferably from about 0.5 to 10 moles of the Hetcrocycle will be utilized per mole of lithium with from about 1 to 5 moles of the Heterocycle per mole of lithium being most preferred.

The polymerization temperature utilized can vary over a broad range of fiom about -20°C to about 150°C hi most cases a temperature within the range of about 30°C to about 125°C will be utilized. The pressure used will normally be sufficient to maintain a substantially liquid phase under the conditions of the polymerization reaction. An advantage of the present polar modifier is that the Heterocyclcs are capable of operating in the range 120 to 150°C and thus facilitating a high-temperature and hence rapid reaction.

The polymerization to form a rubbery polymer relevant to the present invention is conducted for a length of time sufficient to permit substantially complete polymerization of monomers (i.e. Greater than 99% by weight monomer reaction). In other words, the polymerization is nomially carried out until high conversions are attained. The polymerization can then be terminated using a standard tecimique. The polymerization can be terminated with a conventional noncoupling type of terminator, such as water, an acid, a lower alcohol, and the like or with a coupling agent.

The polymerizations of the present invention are carried out in an inert organic solvent hydrocarbon solvent. Thc inert organic solvent can be one or more aromatic, paraffinic, or cycloparaffinic compounds. These solvents preferably will normally contain from 4 to 10 carbon atoms per molecule and will be liquids under the conditions of the polymerization. Some representative examples of suitable organic solvents include pentane, isooctane, cyclohexane, hexane, normal hexane, benzene, toluene, xylene, ethylbenzene, alone or in admixture. Hexane and n-hexane are preferred.

Examples

This invention is illustrated by the following examples which are given for the purpose of illustration and are not to be regarded as limiting the scope of the invention or the manner in which it can be performed.

Experimental conditions All reactions were conducted in oven-dried glassware using anhydrous solvents. Dr, oxygen free heptane was obtained by Solvent Purification System MBRAUN SPS Compact. The H spectra were recorded at room temperature on Bruker Avance 400 (1Il: 400.13 MI-lz) or Varian Mercury 400 Spectrometers (H: 399.96). All chemical shifis are reported in parts per million (?, ppm) with reference to Me4Si (TMS, 0.0). DSC analysis was canied out using TA Instruments D5C2920 System at temperature interval -60°C to +50°C at heat rate of 10°C/minute in a nitrogen atmosphere. Gel-permeation chromatography (GPC) analysis of the polymers was performed on a Yarian PL-GPC5O system with a refractive index detector (tetrahydrofuran (stabilised with 0.025% BHT) as the elucnt, flow ratc I mL/niin at 25°C) using the appropriate Mark Houwink constant (polybutadiene standard). Raman spectra were recorded using Horiba Sobin Yvon DU42OAIOE/325 (25mW) system with the laser wave length 532nm.

Example I

In this experiment a polyisoprene having a high 3,4-vinyl units content was synthesised using 4- [tetrahydro-2-furanyl)rnethyl]rnorpholine (TUFMM) as a polar modifier (PM). In the procedure used an oven dried (at 200°C) 3-necked flask fitted with stirrer gland, thermocouple well, cold finger, septum and stirrer were assembled hot and purged by vacuum/nitrogen. The reaction flask was charged with thy heptane (170g), dried over aluminium oxide and sodium, and distilled-before -use isoprene (27.3g, 0.4mol). Premix was heated to 65°C wider nitrogen blanket. THFMM(0.35g, 0.00 lSmol) was then added via a septum followed by addition O.lml of 2M solution of n-BuLi in cyclohexane for scavenging the premix. Soon after the exotherm was observed 0.3m1 of 2M n-BuLi in cyclohexane was added for polymerisation initiation (molar ratio of polar modifier to initiator was equal to 3). The temperature was kept within 1-2 degrees of 65°C, controlled mainly by cold water bath. The reaction was lefi stirring for 2 hours to ensure the reaction had gone to completion. Polymer from the reaction mixture (92% conversion of isoprene) was precipitated into ethanol containing butylated hydroxytoluene (BHT) as stabilizer, dried under reduced pressure at 30-40°C. The obtained polyisoprene was characterised by 1ll NM K, Raman. GPC, and DSC and was determined to have a microstructure which contained 22% of 1,4-PIP units, 74% of 3,4-PIP units and 5% of 1,2-PIP units and glass transition temperature (Tg) at -1-5.17°C

Example 2

Procedure used in Example 1 was utilised in this example except that tetrameihylethylenediamine (TMEDA) was used as a polar modifier at the same conditions and the same molar ratio of polar modifier to initiator equal to 3. The comparison of properties of obtained polyisoprenes is given below in the Table 1.

Table 1.

Mierostructure (%) Example No Tg, °C _________ ________ _________ 1,4-PIP 3,4-PIP 1,2-PIP 1 +5.17 22 74 5 2 -8.54 29 67 4

Example 3

A dry 1L stainless steel reactor was charged with dry heptane (340g) under nitrogen and heated to 40°C. TH FM M 0.35g, 0.0002mol) and 1 ml of n-BuLi were added to the preheated solvent (molar ratio of polar modifier to initiator was equal to 1). Via a pressure burette, dried over molecular sieves styrene (18.2g. 0.l7mol) and 1,3-butadiene (75.5g. 1.40 mol, moisture content below Sppm) were charged to the reactor under niftogen pressure, allowing the pressure to increase in the reactor to between 5 and 7 bar. The reaction mixture was then heated to 70°C.

and left for 2 hours, taking samples every hour for Ramarn analysis to confirm the random distribution of styrene in the copolymer. The reaction was quenched with ethanol after two hours. Obtained polymer solution was stabilised with BHT, residual solvent removed and polymer dried under reduced pressure to be characterised by Raman, GPC and DSC to confirm physical and chemical properties and was determined to have a niicrostructure which contained 59% of 1,2-PBD units, 24% of 1,4-PBD units and 17% of randomised styrene units with glass transition temperature (Tg) at -41.81°C.

Alternative methods of determining styrene distribution randomness include nuclear magnetic resonance

Examples 4, 5

Procedure used in Example 3 was utilised in these examples except that in Example 4 tetramethylethylenediamine (TMEDA) and in Example 5 2,2-bis(2-tetrahydrofhryl)propane were used as polar modifiers at the same conditions and the same molar ratio of polar modifier to initiator equal to 1. The properties comparison of obtained butadienestyrene copolymer is given below in the Table 2.

Table 2.

Microstructure (%)

Example No T, °C

i,4-czs 1,4-trans 1 2-SSBR Styrene

____________ _______ SSBR SSBR ________ ________

3 -41.81 8 15 59 18 4 -40.67 13 24 43 18 TBC 8 15 59 18 Each of the above polymers resulting from examples ito 5 were washed using water, three times with SOOml in a two phase extraction. Example 1 polymer was found on analysis to comprise little or no detectable polar modifier, whereas examples 2, 3, 4 and 5 comprised detectable levels of polar modifier. Furthermore, the polar modifier could be selectively extracted in a further step, for example using counter current solvent extraction, for reuse the reaction.

A polymer produced by the process of the present invention, as described above preferably comprises a residual [-leterocycle level is in the range Ito 100 part for million. This enables the material to be used as a tracer for establishing a source for the synthetic rubber, such as when tracing environmental contamination. This may enable a user of the material to be ruled out as a source of contamination.

Unless specified otherwise, herein all values of parameters are taken as those measured at 20°C.

Claims

Claims, 1. A process for the synthesis of a rubbery polymer which comprises copolymerizing a diene in an inert organic solvent at a temperature in the range of about 30°C to about 150°C in the presence ofa catalyst system which process compris: (a) an organolithium initiator and (b) one or compounds which are heterocycles containing two heteroatoms, one of which is a nitrogen substituted with a tetrahydroftiran-2-ylmethyl group, those compounds; being selected from the group having the structures A, B, C, D, E or F: iSA B C D E n-n-/ 1 )Fwherein R1 is Ci to C10 alkyl or 6 to 10 aryl; wherein R2 is a bivalent saturated, saturated or unsaturated, hydrocarbon radical of from I to 10 carbon atoms or a bivalent aryl group containing from 6 to 10 carbon atoms and the structures A to F being collectively termed the Heterocycles.
2. The process as specified in claim 1 wherein the molar ratio of the heterocycle or heterocycles to the organolithium initiator is within the range of 0.25 to about 15.
3. The process as specified in claims I or2 wherein from about 0.01 parts per hundred parts by weight of monomer phm] to 0.1 phm of the organolithium initiator is present.
4. The process as specified in any of claims I to 3 wherein the organolithium initiator is an organomonolithium compound.
5. The process as specified in claim 4 wherein the inert organolithium initiator is n-butyl lithium.
6. The process as specified in any preceding claim wherein the inert organic solvent is hexane.
7. The process as specified in any proceeding claim wherein the temperature in the range of 130°C to 150°C.
8. The process as specified in any preceding claim wherein R1 is TI or CH3.
9. The process as specified in any preceding claim wherein the Heterocycle used is A.
10. The process as specified in any of claims 12 8 wherein the Heterocycle used is C, E or F.
ii. The process of claim I for the synthesis of a rubbery polymer which comprises terpolymerizing 1,3-butadiene, isoprene, and styrene in an inert organic solvent at a temperature which is withm the range of about 30° to 150°C in the presence of a catalyst system which comprises: o iS oA B C D E ) 3 n

F

(a) an organolithium initiator and (b) one or compounds which are heterocycles containing two heteroatoms, one of which is a nitrogen substituted with a tetrahydrofuran-2-y!methyl group, those compounds; being selected from the group having the structures A, B, C, D, E or F: wherein R is C1 to C10 alkyl or 6 to 10 my! and the structures A to F being collectively termed the T-leterocyc!es.
12. The process of claim 11 wherein the rubbery polymer is washed using water for the removal of the heterocycle.
13. The process of claim 1, used to synthesise 3,4-polyisoprene which comprises copolyrnerizing isoprene in an inert organic solvent at a temperature in the range of about 30°C to about 150°C in the presence of a catalyst system which comprises (a) n-butyl lithium initiator and (b) one or compounds which are heterocycles containing two heteroatoms, one of which is a nitrogcn substitutcd with a tctrahydroftiran-2-ylmcthyl group, thosc compounds; bcing selected from the group having the structures A, B, C, D, E or F: wherein R is C ito C 10 alkyl or 6 to 10 aryl and the structures A to F being termed the Heterocycles.
14. The process of claim 13 wherein the heterocycle is A.
15. Thc process as specified in claim 13 wherein the Heterocycle used is C, E or F.
16. A polymer produced by the process of any of claims 1, 11 or 13 wherein the residual Heterocycle level is in the range Ito 100 parts per million.