Modification of polymer-lithium coupled with polyhalides
United States Patent Selman Apr. 22, 1975 1 1 MODIFICATION OF POLYMER-LITHIUM [56] References Cited COUPLED WITH POLYHALIDES UNITED STATES PATENTS [75] lnventor: Charles M. Selman, Bartlesville. 2.908.672 10/1959 Jackson 260/942 M Okla. 3.163.630 12/1964 Pampus 260/942 M 3.278.508 10/1966 Kahle et al. 260/942 M [73] Asfignee: Petmleum Cmnvanyv 3.312.680 4/1967 Kahle er al. 260/942 M Bafilesvlller Okla- 3.429.829 2/1969 Kahle et al. 260/942 M 3.542.716 11/1970 Muller 260/942 [22] 1973 3.595.941 7/1971 Farrar 260/880 [21] Appl. No.: 353,453  
  Related U.S. Application Data j &#39;l&#39;f iff&#34;&#34;.&#39;&#34; g &#39;7&#39; [63] Continuation-impart of Sen No. 107,579, Jan. 18, S818 am Jammerfl en&#34; 1971. abandoned.  
  [57] ABSTRACT [52] US. Cl. 260/94.3; 260/83.7; 260/85.l; In the preparation of conjugated diene polymers with 260/935 S; 260/93.5 A; 260/942 M; multilithium initiators followed by termination with 260/94-7 HA; 260/ polyfunctional reagents, broader molecular weight distribution is obtained by modifying the polymerization 1 f Cosd Cosd C08f 19/08 reaction with a magnesium, calcium, strontium, or 1 Fleld of Search 260/942 barium halide or hydrocarbylmetal halide.  
 21 Claims, No Drawings MODIFICATION OF POLYMER-LITHIUM COUPLED WITH POLYHALIDES This application is a continuation-in-part application of copending application Ser. No. 107,579, filed Jan. 18, 1971, now abandoned.  
 FIELD OF THE INVENTION This invention relates to the preparation of conjugated diene polymers.  
  In another aspect, the invention relates to a manner of modifying a polymerization process using multilithium initiators.  
  Another aspect of the invention is a novel initiator system using Group &#34;A metal compound modified multilithium initiators.  
  A broader molecular weight distribution is desired in conjugated diene polymers, including homopolymers, cojugated diene copolymers, and copolymers of conjugated dienes with vinyl aromatic-substituted compounds. Such polymers of broader molecular weight distribution tend to have more desirable processing characteristics such as better bonding on a roll mill, faster and better mixing of compound recipes in an internal mixer, and reduced cold flow.  
  Furthermore, in application to the multilithium initiator prepared conjugated diene polymers, polyfunctional terminating agents which have at least three reactive sites are utilized so as to provide branched polymers of a radial nature. By the use of such coupling agents which also act as terminating agents, cold flow of the diene polymer is reduced, and processing properties generally improved over the uncoupled polymer, yet gel formation frequently is a problem when such reagents are used.  
 OBJECTS OF THE INVENTION It is an object of my invention to provide a method of modification of a lithium initiated polymerization process so as to broaden molecular weight distribution of the resulting polymer.  
  A further object of my invention is to provide a novel modifier system for multilithium initiators for conjugated diene polymerization processes.  
  A further object of my invention is the reduction of gel in the coupling of conjugated diene polymers with polyfunctional terminating agents.  
 SUMMARY OF THE INVENTION I have discovered that polymerization reactions initiated with multilithium initiators, particularly those subsequently terminated with polyfunctional terminating agents, can be modified effectively by using halides of Group &#34;A metals, or by using Group IIA organometal halides. The Group IIA metal should have an atomic number of at least 12. The polymer resulting from the process using my modifiers has a broadened molecular weight distribution and can be more effectively coupled in a termination step without production of gel.  
 DETAILED DESCRIPTION OF THE INVENTION My additives or modifiers can be represented by the general formula R MX In this formula R is a hydrocarbyl radical containing from 1 to 20 carbon atoms and can be alkyl, cycloalkyl, aryl, and combinations thereof such as alkaryl, aralkyl, and alkylcycloalkyl. i prefer the alkyl radicals in general, and more preferably those in which the alkyl has up to about 10 carbon atoms per R group. M is a metal of Group &#34;A of the Periodic Table with an atomic number of at least 12 and is magnesium, calcium, strontium, or barium. X is a halogen, and can be fluorine, chlorine, bromine, or iodine. The Periodic Table is as shown in the Handbook of Chemistry and Physics, 49th Edition, The Chemical Rubber Co. (l968-l969) page B-3.  
  In the R,,MX,, modifiers, a is either 0 or I, of course, since the metal halides themselves are effective modifiers. The other integer designator, b, will be either I or 2, necessarily being I when a is l, or 2 when a is 0. When b is 2, then X is not limited to a single halogen, but could represent two differing halogen atoms in the molecule.  
  Examples of suitable R MX modifiers include barium chloride, barium iodide, n-butylbarium fluoride, magnesium chloride, magnesium bromide, magnesium iodide, methylmagnesium chloride, cyclohexylmagnesium bromide, eicosylmagnesium iodide, phenylmagnesium bromide, benzylmagnesium chloride, 4-tertbutylcyclohexylmagnesium fluoride, 3-phenylcyclopentylmagnesium chloride, nbutylcalcium iodide, eicosylcalcium bromide, calcium chloride, calcium bromide, calcium fluoride, calcium iodide, phenylstrontium chloride, cyclohexylstrontium bromide, strontium bromide, ethylbarium chloride, phenylbarium bromide, barium fluoride, and the like.  
  These modifiers are used in polymerizations initiated with multilithium initiators. The multilithium initiators can be represented by the general formula R&#39;Li,. R is a polyvalent hydrocarbyl radical with a valence equal to the value of x, and x is an integer of from 2 to 6 inclusive. R can be an aliphatic, cycloaliphatic, or aromatic radical, and can contain from i to 20 carbon atoms per polyvalent hydrocarbyl radical.  
  Preferred multilithium initiators are those obtained by the reaction of lithium or an organomonolithium compound such as n-butyllithium or sec-butyllithium with a divinyl aromatic hydrocarbon such as 1,4- divinylbenzene or 1,4-divinylnaphthalene which can, if desired, be in the presence of a small amount of a solubilizing conjugated diene of from 4 to 12 carbon atoms per such diene.  
  Other suitable multifunctional lithium. initiators include the lithium metal adducts of conjugated dienes such as isoprene or other diene of 4 to 12 carbon atoms, or the dilithium adducts of fused-ring aromatic hydrocarbons such as naphthalene or other aromatic hydrocarbons of from about 12 to 30 carbon atoms.  
  Suitable polylithium compounds include 9,10-dilithioanthracene; 2,2&#39;,2&#34;-trilithio-p-terphenyl; 1,12-dilithiododecane; 1,2-dilithiol ,2-diphenylethane; 1,4-dilithiocyclohexane; and the like.  
  The amount of my R,,MX,, additive or modifier employed according to my invention can vary widely, depending on the degree of modification desired, the type of polymerization, whether a polar compound is employed as randomizing agent, and the like. The amount of modifier employed according to my invention can be expressed in terms related to the amount of the multilithium initiator used in the polymerization process. The initiator itself normally is employed in an amount of from 0.1 to milliequivalents of lithium per 100 grams of monomer or monomers employed.  
  The amount of modifier employed generally is from 1.25 to 10 millimoles of modifier per milliequivalent of lithium in the initiator employed for homopolymerization of a conjugated diene, or copolymerization of two or more conjugated dienes; or for block copolymerization processes employing one or more conjugated dienes with one or more copolymerizable monovinylsubstituted aromatic hydrocarbons, i.e., in the absence of a polar compound randomizing agent. I presently prefer to employ not less than about 2.5 meq, milliequivalents of lithium per 100 g of monomer(s) employed in such polymerizations.  
  When employing a random copolymerization process employing one or more conjugated dienes with one or more monovinyl-substituted aromatic hydrocarbons in the presence of a polar compound as a randomizing agent, the amount of modifier employed can range lower, generally from about 0.75 to millimoles of modifier per milliequivalent of lithium in the initiator employed. I presently prefer, in such random copolymerizations, to employ not less than about 1.5 meq of lithium.  
  I have found, with either type of polymerization, that to prepare gelfree coupled polymers that it is desirable to use toward the higher ratio of the range relative to the amount of lithium charged as the amount of lithium itself is reduced. In other words, as the amount of lithium approaches the lower end of the utilizable range, the amount of modifier utilized should be increased toward the higher range.  
  The modifiers of my invention can be charged to the polymerization mixture prior to initiation of polymerization, or during the polymerization reaction but prior to substantial completion of the polymerization reaction. My additives or modifiers can be charged initially, or incrementally during a portion of or all of the polymerization reaction, or continuously during a portion of or during substantially all of the polymerization reaction interval. Of course, a portion of the additive amount employed can be added prior to initiation, the remainder in one or more portions incrementally or continuously after polymerization is commenced. By prior to substantial completion of the polymerization reaction, as the phrase is employed herein, I mean prior to about 75 weight percent conversion of monomer or monomers present in the polymerization reaction. It presently is preferred that the modifier be charged initially, e.g., before addition of or substantially with, or very shortly after addition of the initiator to the polymerizable monomers. Appreciable delay in addition of the modifier to the polymerization system in some instances results in gel in the coupled polymers rather than gel-free coupled polymers.  
  The monomers which can be employed in a process according to my invention are those known to polymerize with lithium initiator systems. Such monomers include the particularly useful conjugated dienes of from 4 to 12 carbon atoms per molecule, preferably those of from 4 to 8 carbon atoms per molecule, as well as the vinyl-substituted aromatic compounds of from 8 to carbon atoms per molecule, preferably those of from 8 to 12 carbon atoms per molecule. Copolymers of conjugated dienes with vinyl-substituted aromatic compounds also can be prepared according to the process of my invention modified with my modifiers.  
  Examples of suitable monomers include the preferred butadiene, isoprene, styrene, and copolymers of any two thereof, as well as 2,3-dimethyl-l,3-butadiene, piperylene, 3-butyl-l ,3-octadiene, Z-phenyl-l ,3-  
 butadiene, l-vinyl-napthalene, 3-methylstyrene, 4- cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4- benzylstyrene, 4-tert-butylstyrene, 4-isopropylstyrene, and the like. Not only can mixtures of two or more monomers be employed, but sequential addition of and hence sequential polymerization of different monomers also can be utilized with the initiators modified with my modifiers.  
  Polymerization temperature generally employed will be from -50 C. to 150 C., more usually from l0 C. to +75 C. Pressures employed usually are at least sufficient to maintain a substantial portion of the reaction mixture in a liquid phase. It is preferred that the polymerization reactions be carried out in the presence of a suitable diluent, usually inert hydrocarbon compounds containing from 4 to 12 carbon atoms per molecule or mixtures thereof. Mixtures of hydrocarbons with polar compounds such as ethers, thioethers, and tertiary amines of from 2 to 30 carbon atoms per molecule, also are suitable.  
  Various other prior art additives can be used within the process, such as the alkali metal alkoxides to promote the formation of random copolymers of conjugated dienes and vinyl aromatic hydrocarbons when mixtures of such monomers are polymerized with multilithium initiators and hydrocarbon diluents such as by the process described in U.S. Pat. No. 3,294,768, issued Dec. 27, 1966, to C. F. Wofford.  
  The polymers produced according to the process of my invention using multilithium initiators with the polymerization process modified by the organometal halides or metal halides of Group IIA are coupled with agents as described in U.S. Pat. No. 3,281,383 issued Oct. 25, 1966, to R. P. Zelinski and Henry L. I-Isieh. The polyfunctional treating agents are added to the unquenched polymerization reaction mixture, preferably as soon as feasible after the polymerization reaction is substantially complete, i.e., the desired degree of conversion of monomers has been reached. Such coupling agents must be added prior to the addition of any other material such as water, acid, alcohol, or other material tending to inactivate or remove active lithium atoms present in the polymer, though minor amounts often are present with the coupling agent and are not objectionable. Temperature of the coupling reaction can vary over a broad range, and is conveniently that used for the polymerization itself. Temperatures above about 35 C. are preferred for more rapid reaction, since, under such conditions, reaction normally occurs as soon as materials are blended and the time is quite short being from one minute to one hour approximately. Longer reaction intervals are satisfactory, and  
 often are required at lower temperatures. However, relatively long reaction times at elevated temperatures, e.g., such as one hour at C., are to be avoided, since gelled polymer can result in some instances. One skilled in the polymer arts can readily adjust time and temperature of coupling my modified polymerizations to reach the desired gel-free coupled polymers.  
  The polyfunctional treating agent itself contains at least three reactive sites which are capable of reacting with a lithium carbon bond in the polymer, and thereby resulting in the coupling of the reagent to the polymer. These treating agents include polyepoxides, polyisocyanates, polyimines, poly aldehydes, polyketones, polyanhydrides, polyesters, polyhalides. Mixtures of two or more such coupling agents can be utilized where desired.  
  While any polyepoxide can be used, preferred are those which are liquid since they can be readily handled and also since they form a relatively small nucleus for the radial polymer. Especially preferred among the polyepoxides are the epoxidized hydrocarbon polymers such as epoxidized liquid polybutadiene andthe epoxidized vegetable oils such as epoxidized soybean oil and epoxidized linseed oil. Other epoxy compounds such as 1,2;5,6;9,IO-tri-epoxydecane, and the like, also can be used.  
  The polyisocyanates are preferably those compounds represented by the formula R&#34;(NCO),,, where R&#34; is a polyvalent organic radical which can be aliphatic, cycloaliphatic, or aromatic, and contains from 2 to 30 carbon atoms, and m is an integer of 3 or more, preferably 3 or 4. Examples of such compounds include benzene-l ,2,4-triisocyanate, naphthalene-1,25,7- tetraisocyanate, triphenylmethane-triisocyanate, naphthalene-1 ,3,7-triisocyanate, and the like. Especially suitable is a commercially available product known as PAPI-l. This material is a polyarylpolyisocyanate having an average of 3 isocyanate groups per molecule and an average molecular weight of about 380. Structurally the compound can be represented by a series of isocyanate-substituted benzene rings joined through methylene linkages.  
  The polyimines which are also known as polyaziridinyl compounds preferably are those containing 3 or morea ziridine rings as represented by the formula:  
 wherein each R can be hydrogen, or an alkyl, aryl or cycloalkyl radical or combination of such hydrocarbon radicals, the total of the R&#39; groups containing up to carbon atoms. The aziridine rings can be attached to a carbon, phosphorous or sulfur atom. Examples of these compounds are the triaziridinyl phosphine oxides or sulfides such as tri( 1-aziridinyl)phosphine oxide, tri(2- methyl-l-aziridinyl)phosphine oxide, tri(2-ethyl-3- decyll -aziridinyl)phosphine sulfide, tri(2-phenyll aziridinyl)phosphine oxide, tri(2-methyl-3-cyclohexyll-aziridinyl)phosphine sulfide, and the like. Also suitable are the triaziridinyl substituted triazines and the triphosphatriazines containing 3, 4, 5 or 6 aziridinyl substituted rings. Examples of these compounds indride, styrene-maleic anhydride copolymer, and the like. Examples of the polyesters include the glycerol tristearates, glycerol trioleates and similar compounds.  
  Among the polyhalides, preferred are the silicon tetrahalides such as silicon tetrachloride, silicon tetrabromide and silicon tetraiodide, and the trihalosilanes such as trifluorosilane, trichlorosilane, trichloroethylsilane, tribromobenzylsilane, and the like. Also preferred are the polyhalogen substituted hydrocarbons such as 1,3,- 5-tri(bromoethyl)-benzene, 2,5,6,9-tetrachloro-3,7- decadiene, and the like, in which the halogen is attached to a carbon atom which is alpha to an activating group such as an ether linkage, a carbonyl group, or a carbon-to-carbon double bond. Substituents which are inert with respect to lithium atoms in the terminally reactive polymer also can be present in the active halogen containing compounds. Alternatively, other suitable reactive groups different from the halogen as described above can be present. Examples of compounds containing more than one type of functional group include l,3-dichloro-2-propanone, 2,2-dibromo-3- decanone, 3,5,5-trifluoro-4-octanone, 2,4-dibromo-3- pentanone, l,2;4,5-diepoxy-3-hexanone, 1,2,;1 1,112- diepoxy-8-pentadecanone, 1,3;1 8,19-diepoxy-7,&#39;l 4- eicosanedione, and the like. Specifically preferred polyfunctional terminating agents include silicontetrachloride, stannic chloride, and polyepoxidessuch as epoxidized linseed oil.  
  The amount of polyfunctional treating agent used is in the range of from 0.] to 1.5 equivalents of the treating agent per equivalent of lithium present in the polymer. The optimal amount for maximum branching is 1 equivalent of treating agent. Larger amounts can be employed, if desired, since such usage encourages the production of polymers containing terminally reactive groups, or encourages coupling only the linear polymer instead of branched polymer. Lower molecular weight linear polymer can be produced along with higher molecular weight radial polymer when the amount of treating agent is insufficient to provide maximum branching.  
  After the polymers have been reacted with the polyfunctional compound, the resulting coupled polymer can be recovered by any means known by the art, such as by treatment with materials containing active hydrogen including alcohol, acid, or mixtures of such reagents.  
 EXAM PLES The following examples demonstrate the use of the modifiers according to my invention. The examples, and specific reactants used therein, are intended to be illustrative of my invention, and not limitative of the scope thereof.  
 EXAMPLE I Runs were made in which 1,3-butadiene was polymerized with a multilithium compound. The multilithium compound was prepared by reacting divinylbenzene with&#39;sec-butyllithium at a mole ratio of 0.55:1 respectively. Certain of the runs were made according to the invention in that a modifier of the invention, magnesium chloride, also was present in the polymerization system. Suitable control runs were made. Some of the runs were terminated with a polyfunctional agent, silicon tetrachloride, as a part of the procedure of this invention. The properties of the polymers obtained from each of these runs were then determined.  
 Polyermization Recipe Parts by Weight Cyclohexane 975 1,3-Butadiene 100 Multilithium compound (mehm&#34;&#39; (2.5) MgCl variable Temperature. C 70 Time. hours 2 Silicon tetrachloride variable &#34;mehm milliequivalents of lithium per 100 g of mnnomefls).  
  In each of the runs, cyelohexane was charged to the reactor first followed by butadiene. The multilithium initiator next was charged, followed by the magnesium chloride 0.25 M in toluene diluent. The temperature was adjusted to 70 C. and the polymerization reaction continued for 2 hours. To certain of the runs furtherparts by weight of the polymer. Each polymerization mixture was coagulated with isopropyl alcohol and the polymer separated and dried. The results of these runs are shown below in Table 1.  
 pared in the presence of MgC1 but without SiC1 termination. Run 2 demonstrates the properties of a polymer prepared with a multilithium initiator in the absence of an additive of my invention but terminated with SiCl Runs 10, l l, and 12 illustrate the desirability of avoiding too long a coupling time at elevated coupling temperatures.  
 The results in Table I, runs 4 through 9 inclusive,  
 clearly demonstrate that the use of a modifier, MgCl of this invention provides a gel-free polymer with a broadened molecular weight distribution, i.e., larger heterogeneity index than a polymer made in the absence of an additive according to my invention.  
 EXAMPLE 11 Additional runs were conducted in which butadiene was polymerized with the multilithium initiator as described in Example 1.  
 Polymerization Recipe Parts, by weight Cyclohexane 780 1,3-Butadiene 100 Multilithium compound (mehm) 3.0&#34;&#34;  
 MgCl (0.7M in toluene diluent) Temperature, C  
 Time, hours 2 Silicon tetrachloride variable variable &#34;&#34;except runs 21-23 inclusive employing only 2.0 mehm initiator.  
 The charging procedures and polymer isolationprocedures in these runs were the same for Runs&#39;1 &#39;3fto 17 inclusive as those employed in Example 1. Thefcharging and isolation procedures for Runs 18-19 also were the Table 1 Modifier Polyfunctional Agent Hetero- Run MgC1 SiClJ&#34; Ratio&#34;&#34; lnherent Ge1&#34; geneity No. mhm mhm MgCl zLi Viscosity Index &#34;Ratio of millimoles of MgCl, per milliequivalent of lithium in the initiator charged.  
  &#39;Determined according to the procedure of U.S. Patent 3.278.508, Col. 20. notes a and b.  
 &#34;The ratio of weight average molecular weight (Mw) to number average molec gel permeation chromatography (GPC).  
 &#34;&#34;mhm gram millimolcs per g of monomer(s).  
 &#39;&#34;Determined on the soluble in tetrahydrofuran) portion of the polymer.  
  Runs 1, 2, and 3 of Table 1 are control runs. Run 1 demonstrates the properties of a polymer prepared in the absence of MgCl addition and SiC1 termination. Run 3 demonstrates the properties of a polymer preular weight (Mn) as determined by same as for Example 1 except that the addition of the modifier was delayed until after substantial polymerization had occurred. The results of these runs are shown below in Table 11.  
 Table I1-Continued Run MgCl SiCl Ratio Inherent Gel Heterogeneity No. mhm mhm MgCl :Li Viscosity Index The results in Table 11 again demonstrate that the use Table IV of an additive of this invention provides a gel-free polymer of broad molecular weight distribution. The results further show the desirability of using a proper ratio of MgCl zLi so that gel-free polymers may be produced. Runs 1820 inclusive further indicate that the modifier preferably is added initially to the polymerization reaction mixture as in Runs 13-17 inclusive. Runs 2l23 inclusive further illustrate that in these types of polymerizations conducted in the absence of a polar compound as randomizer, that it is preferable to adjust the level of multilithium initiator employed in order to reach the desired gel-free coupled polymer.  
 EXAMPLE 111 Additional runs were conducted in which butadiene was copolymerized with styrene in the presence of a multilithium initiator and a randomizing agent.  
 Polymerization Recipe Parts by Weight Cyclohexane 624 1,3-Butadiene 75 Styrene 25 Multilithium Initiator (mehm) variable Potassium-tert-butoxide (0.09 N in toluene) variable MgCl (0.7 N in toluene diluent) variable Temperature C. Time, hours 2 Silicon tetrachloride variable Table 111 Run M gC l SiCl, Ratio Inherent Gel No. mhm mhm MgCl :Li Viscosity 7:  
 &#34;SiCl, did not appear to mix well with this reaction mixture.  
 (Using 1.75 mehm multilithium initiator, and 0.17 mhm potassium-tert-butoxide) Run MgCl SiCl. Ratio Inherent Gel No. mhm mhm MgCl iLi Viscosity &#34;&#34;SiCL did not appear to mix well with this reaction mixture.  
 normally employed compounding recipes so as to provide molded rubber articles, and the like. Formulations can contain carbon black, or other reinforcing agents, as well as extending materials such as various extender oils and plasticizers. These polymers can be employed in admixture with other polymers, rubbery or plastic in nature, depending upon the final use intended.  
  In my description, including examples, I have shown the beneficial results obtained from the modified polymerization process according to my invention, using the modifiers as described. Variations and modifications of my invention can be made, as will be apparent to one skilled in the art, yet without departing from the intended scope and spirit of my diclosure including the claims as here appended.  
 1 claim:  
  1. In a process for preparing gel-free coupled poly mers wherein at least one polymerizable monomer is polymerized with a multilithium initiator and wherein a polyfunctional coupling agent containing at least three reactive sites capable of reacting with a lithiumcarbon bond in a polymer is added in an effective amount to the polymerization reaction after initiation of said polymerization of said monomer with said multilithium initiator and prior to quenching of said polymerization reaction, thereby coupling said polymer, and wherein said polymerizable monomer-is at least one conjugated diene, at least one monovinyl substituted aromatic compound, or both, the improvement which comprises the addition to the polymeriza tion reaction, after charging of said polymerizable monomer and said multilithium initiator, of a Group 11A metal halide or hydrocarbylmetal halide modifier wherein the Group 11A metal thereof is magnesium, calcium, strontium, or barium, and wherein said modi= fieris employed in a range of about 1.25 to 10 millimoles of said modifier per equivalent of lithium in said multilithium initiator;  
 wherein said multilithium initiator is a lithium metal adduct of a conjugated diene, a dilithium adduct of a fused ring aromatic hydrocarbon, or is represented by R&#39;Li, wherein R is a polyvalent hydrocarbyl radical with a valence equal to the value of X. 2. The process according to claim 1 wherein said modifier is added to said polymerization reaction at least one of incrementally and substantially continuously during at least a portion of said polymerization reaction.  
  3. The process according to claim 1 wherein said modifier can be represented by R,,MX,, wherein each R ,represents a hydrocarbyl radical containing up to 20 carbon atoms and each R is individually selected from alkyl, cycloalkyl, aryl, or combination, M is said metal of Group IIA, X is a halogen and is fluorine, chlorine, bromine, or iodine, a b equals 2 and a is or 1, and wherein said polyfunctional treating agent is added to said polymerization reaction after polymerization of said monomer with said multilithium initiator is substantially complete and prior to quenching.  
  4. The process according to claim 3 wherein said polyfunctional coupling agent containing at least three reactive sites is a polyepoxide, polyisocyanate, polyimine, polyaldehyde, polyketone, polyanhydride, polyester, polyhalide, or mixture, and is employed in a range of 0.1 to 1.5 equivalents of said polyfunctional treating agent per equivalent of lithium.  
  5. The process according to claim 1 employing at least about 2.5 milliequivalents of lithium per 100 gram of monomer employed in such polymerization.  
  6. A process according to claim wherein said polymerization reaction is carried out in the presence of a diluent selected from hydrocarbons containing 4 to 12 carbon atoms per molecule, ethers, thioethers, tertiary amines of 2 to 30 carbon atoms per molecule, and mixtures thereof.  
  7. A process according to claim 3 wherein further is employed in said polymerization reaction an alkali metal alkoxide.  
  8. The process according to claim 4 wherein said multilithium initiator is said R&#39;Li, wherein R contains up to carbon atoms, has a valence equal to x, and is aliphatic, cycloaliphatic, aromatic, or combination, x is an integer of 2 to 6 inclusive, and wherein said multilithium initiator is employed in said polymerization process in an amount of 0.1 to 100 milliequivalents of. lithium per 100 grams of polymerizable monomer.  
  9. The process according to claim 8 wherein said polymerizable conjugated diene contains 4 to 12 carbon atoms per molecule and said polymerizable vinylsubstituted aromatic compound contains 8 to 20 carbon atoms per molecule.  
  10. The process according to claim 9 wherein said polyepoxides are liquid epoxidized hydrocarbon polymers; said polyisocyanates can be represented by the formula R&#34;(NCO),,, wherein R&#34; is a polyvalent organic radical and is aliphatic, cycloaliphatic, or aromatic, containing from 2 to carbon atoms, and m is an integer of at least 3; said polyimines&#39; can be represented by the formula C lll N wherein each R&#39; is hydrogen, alkyl, aryl, or cycloalkyl radical, or combination, such that the total of R&#39; groups contain up to 20 carbon atoms.  
  11. A process according to claim 10 wherein said R MX is R MgX 12. The process according to claim 11 wherein said polyfunctional treating agent is silicon tetrahalide.  
  13. The process according to claim 12 wherein said multilithium initiator is a reaction product of divinylbenzene and sec-butyllithium, said modifier is magnesium chloride, and said monomer is 1,3-butadiene.  
  14. The process according to claim 9 wherein said polymerization reaction is conducted at a temperature of 50 C. to +150 C., under a pressure sufficient to maintain at least a portion of the polymerization reaction mixture in a liquid phase.  
  15. In a process for preparing gel-free coupled polymers wherein at least one polymerizable monomer is polymerized with a multilithium initiator and wherein a polyfunctional coupling agent containing at least three reactive sites capable of reacting with a lithiumcarbon bond in a polymer is added to the polymerization reaction in an effective amount after initiation of said polymerization of said monomer with said multilithium initiator and prior to quenching of said polymerization reaction, thereby coupling said polymer, and wherein said polymerizable monomer is at least one conjugated diene, at least one monovinyl-substituted aromatic compound, or both, the improvement which comprises the addition to the polymerization reaction, after charging of said polymerizable monomer and said multilithium initiator, of a Group IIA metal halide or hydrocarbylmetal halide modifier in an amount effective to broaden the molecular weight distribution of said coupled polymer, wherein the Group &#34;A metal thereof is magnesium, calcium, strontium, or barium;  
 wherein said multilithium initiator is a lithium metal adduct of a conjugated diene, a dilithium adduct of a fused ring aromatic hydrocarbon, or is represented by RLi, wherein R is a polyvalent hydrocarbyl radical with a valence equal to the value of V 16. The process according to claim 15 employing as said polymerizable monomer at least one polymerizable conjugated diene and at least one copolymerizable monovinyl-substituted aromatic hydrocarbon, said polymerization is a random polymerization conducted in the presence of a randomizing amount of a polar organic compound randomizing agent, and wherein said modifier is employed in the range of about 0.75 to 10 millimoles of said modifier per equivalent of lithium in said multilithium initiator.  
  17. The process according to claim 16 employing said multilithium initiator in an amount sufficient to provide at least about 1.5 milliequivalents of lithium per grams of monomer.  
 18. The process according to claim 17 wherein said polymerizable monomer is butadiene and styrene, said randomizer is potassium tert-butoxide, and said polyfunctional treating agent is silicon tetrachloride.  
  20. The process according to claim 19 employing said multilithium initiator in an amount sufficient to provide at least about 2.5 milliequivalents of lithium per grams of monomer.  
  21. The process according to claim 20 wherein said polymerizable monomer is butadiene, and said polyfunctional treating agent is silicon tetrachloride.  
 UNITED sTATEs PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,879,366 DATED April 22, 1975 INVENTOR(S) Charles M. Selman It i5 certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:  
 Column 11, claim 6, line 36, delete &#34;5&#34; and insert 1h Signed and Sealed this sixteenth Day Of September 1975 [SEAL] Arrest:  
 RUTH C. MASON C. MARSHALL DANN Allesling Officer (ummissr&#39;uncr uj&#39;Parenls and Trademarks