Abstract: A process for preparing a particulate vinyl polymer resin and vinyl polymer resin derived therefrom wherein, comprising polymerization in the presence of a dispersant or graft dispersant having no ionic side groups, optionally containing terminal functional groups, said dispersant is derived from repeating units of .alpha.,.beta.-unsaturated ester(s) of acrylic and/or methacrylic acid and having a molecular weight average of from about 500 to about 50,000.

Abstract: Molded bodies in the form of packing bodies comprising a macroporous strongly acid or basic ion exchange resin having a voids fraction of 5-95 vol % of the macro shape without pores, a BET surface area of 0.1-1,000 sq m/g, and an ion exchange capacity of 0.05-10 meq/g.

Abstract: A toner composition comprised of multiblock or liquid glass resin particles with a glass transition temperature of between from about 20.degree. C. to about 65.degree. C., and pigment particles.

Abstract: A novel rubbery polymer suitable for use in tire tread formulations is characterized in that the polymer comprises polymer particles which have from 2 to 6 domains, each domain comprising from 100 to about 40 weight percent of at least one C.sub.4 to C.sub.8 conjugated diolefin monomer, from 0 to about 60 weight percent of at least one C.sub.3 3 to C.sub.6 alkenyl nitrile monomer and from 0 to about 60 weight percent of at least one C.sub.8 to C.sub.12 monovinylidene aromatic monomer for a total of 100 weight percent of the domain, the monomer composition and/or molecular weight of one domain of each polymer particle differing from the monomer composition and/or molecular weight of each of the other domains of the polymer particle. A process for the production of the rubbery polymer is provided together with a rubber composition comprising the rubbery polymer and at least one diene-based polymer.

Abstract: It has been unexpectedly discovered that various compounds, such as alkyl tetrahydrofurfuryl ethers, can be used to modify anionic polymerizations of conjugated diene monomers. These modifiers can be used to polymerize isoprene monomer into high 3,4-polyisoprene at excellent polymerization rates. This is in contrast to the modifiers such as tetramethylethylene diamine which are typically used to modify such polymerizations. This invention more specifically discloses a process for the synthesis of 3,4-polyisoprene which comprises polymerizing isoprene monomer in an organic solvent in the presence of a catalyst system which is comprised of (a) a lithium initiator and (b) ethyltetrahydrofurfuryl ether.

Abstract: A continuous process is described for preparing copolymer compositions of 1,3-conjugated dienes and aromatic vinyl compounds having a weight average molecular weight of greater than about 100,000, and in one embodiment above about 900,000. The process comprises:(A) continuously introducing into a reactor, a 1,3-conjugated diene, an aromatic vinyl compound, a hydrocarbon solvent and a polymerization catalyst comprising a trimetalated 1-alkyne wherein the catalyst is obtained by reacting at a temperature of above about 70.degree. C., a 1-alkyne containing at least 4 carbon atoms, an organo metallic compound, R.degree.M and a 1,3-conjugated diene wherein the alkyne is characterized by the formulaRCH.sub.2 C.tbd.CH (II)wherein R is an alkyl group, R.degree. is a hydrocarbyl group, M is an alkali metal, the mole ratio of R.degree.

Abstract: The invention concerns preparation of porous copolymer beads by a seeded polymerization process employing gel copolymer seed particles. The process comprises initially providing a plurality of gel-type copolymer seed particles prepared by polymerization of at least one first monovinylidene monomer and a first cross-linking monomer. A second monomer mixture comprising at least one second monovinylidene monomer, a second cross-linking monomer, and a phase-separating diluent is thereafter imbibed by the seed particles and polymerized therein. The process is characterized by selecting the first monovinylidene monomers such that the phase-separating diluent and second monovinylidene monomers are capable of being imbibed by the seed particles in an amount sufficient to form a porous copolymer. The porous copolymer beads produced have stable polymeric structures and good physical properties that render them useful in preparing ion-exchange resins and polymeric adsorbents.

Abstract: There is disclosed a linear block copolymer comprising at least one triblock I-B-I, wherein I is a block of at least one polymerized conjugated diene of at least five (5) carbon atoms, such as isoprene, and B is a block of a polymer of at least one conjugated diene, different from that used to polymerize the block I, of at least four (4) carbon atoms, such as 1,3-butadiene. The B block is selectively hydrogenated, while each of the I blocks is unhydrogenated and therefore retains a sufficient amount of its original unsaturation to vulcanize the copolymer. There is also disclosed an alternative linear block copolymer containing at least one triblock of the first polymer block made from a minor proportion of at least one aryl-substituted olefin, such as styrene, and a major proportion of at least one conjugated diene used to polymerize the block I, the second middle polymer block of at least one diene used to polymerize the block B, and the third polymer block which is the same as the first polymer block.

Abstract: A toner resin suitable for being used in toner compositions or developer compositions for electrostatic imaging is prepared by polymerization of styrene and butadiene in the presence of a mixture of n-dodecyl mercaptan and t-dodecyl mercaptan. The toner resin has defined weight average and number average molecular weights and a defined polydispersity that provide an improved toner resin that can be attained without blending different copolymers while using conventional apparatus. Additionally, the toner resin can exhibit a suitable melt index and glass transition temperature.

Abstract: A process for forming a copolymer of butadiene and other monomers such as styrene is disclosed wherein the final product is characterized by a low residual butadiene content. The process comprises: (a) charging a reaction vessel with butadiene and styrene; (b) initiating said copolymerization reaction; (c) after the exotherm phase of said reaction, purging said reaction vessel with an inert gas while heating said reaction vessel to a final polymerization temperature.

Abstract: This is an improvement upon a process which comprises anionically polymerizing monomers with an anionic polymerization initiator in a suitable solvent thereby creating a living polymer. The improvement comprises terminating the polymerization by the addition of a terminating agent selected from the group consisting of hydrocarbons containing a C-H group where the carbon is connected directly to a triply-bound carbon, hydrocarbons containing a C-H group where the carbon is connected directly to two doubly-bound carbons and hydrocarbons containing a C-H group where the carbon is connected directly to at least 2 aromatic rings, whereing none of said hydrocarbons contain additional aliphatic unsaturation.

Abstract: An improved process for the production of conjugated alkadiene-based polymers of higher vinyl content employs as a structure modifier a compound of the formula ##STR1## wherein R is alkylene, R' alkyl and R" is hydrogen or hydrocarbyl.

Abstract: A process for shortstopping a free radical polymerization of a conjugated diene and optionally a vinyl-substituted aromatic in an aqueous emulsion, using a hydroperoxide as initiator and a redox activator, comprising a divalent transition metal, a reducing agent and optionally being carried out in the presence of a modifier, and being performed by using as sole shortstopping agent an alkali metal polysulphide. This process results in the production of polymeric products which are free of carcinogenic nitrosamines.

Abstract: A suspension polymerization process for the preparation of a polymeric material formed from at least two monomers, a non-gaseous monomer and a gaseous monomer. The composition of the beads or particles of the polymeric material is controlled by adding gaseous monomer to the vapor phase after polymerization of about 5% to about 90% by weight of the non-gaseous monomer or by removing a portion or substantially all of the gaseous monomer in the vapor phase before polymerization of about 70% by weight of the gaseous monomer in the aqueous suspension, or a combination thereof.

Abstract: The subject invention relates to a process for synthesizing random styrene-isoprene copolymers having a medium vinyl microstructure. These random styrene-isoprene rubbers have physical properties which make them highly desirable for utilization in tire tread rubber compounds. The utilization of such random styrene-isoprene rubbers in tire tread rubber results in improved tread wear, rolling resistance and traction characteristics. This invention more specifically relates to a process for preparing a random styrene-isoprene rubber having a medium vinyl microstructure which comprises copolymerizing isoprene and styrene in the presence of (a) at least one organolithium compound and (b) at least one modifier slected from the group consisting of 1,2-dipiperidinoethane, dipiperidinomethane, and tripiperidinophosphine oxide.

Abstract: Disclosure is herein made of a rubber composition containing at least 30% by weight of a butadiene copolymer which is characterized in that: (i) the content of vinyl bonds in a polybutadiene portion is from 40 to 70%; (ii) the content of bound vinyl aromatic compound is from 25 to 50% by weight: (iii) the ratio Mw/Mn between the weight average molecular weight (Mw) and the number average molecular weight (Mn) when calculated as polystyrene according to the gel permeation chromatograph (GPC) method is from 1.8 to 5, and the distribution of the molecular weight is unimodal; (iv) the rate of the copolymer having the weight average molecular weight of not more than 100,000 when calculated as polystyrene is from 10 to 30%; (v) the rate of the copolymer having the weight average molecular weight of not less than 2,000,000 when calculated as polystyrene is from 10 to 30%; and (vi) the Mooney viscosity (ML.sub.1+4 100.degree. C.) is from 20 to 100.

Abstract: Process for the preparation of polymers which comprises a suspension free radical polymerization of monomers in the presence of the initiator O,O-t-amyl-O-(2-ethylhexyl)monoperoxycarbonate.

Abstract: A rubber composition comprising 100 parts by weight of a rubber component which comprises at least 30% by weight of an emulsion polymerization rubber which is a conjugated diene polymer rubber or conjugated dienestyrene copolymer rubber obtained by emulsion polymerization, has a bound styrene content of 0-65% by weight, contains 20-35% by weight of a component having a molecular weight of not more than 150,000 as measured by a gel permeation chromatography and has a Mooney viscosity, ML.sub.1+4 (100.degree. C.), of 60-160 and a Mooney viscosity difference (.DELTA.MV) of -20 to +5 as defined by the following equation:.DELTA.MV=ML.sub.1+4 (100.degree. C.)-ML.sub.1+15 (100.degree. C.)and 45-200 parts by weight of carbon black. Said rubber composition is excellent in abrasion resistance, breaking strength and high histeresis property in uses in which carbon black or oil is blended at a high-filling rate.

Abstract: This is an improvement upon a process which comprises anionically polymerizing monomers with an anionic polymerization initiator in a suitable solvent thereby creating a living polymer. The improvement comprises terminating the polymerization by the addition of a terminating agent selected from the group consisting of boranes, ammonia, halogens, hydrocarbons containing a C-H group where the carbon is connected directly to a triply-bound carbon or to two doubly-bound carbons and silanes.

Abstract: There is disclosed a linear block copolymer comprising at least one triblock I-B-I, wherein I is a block of at least one polymerized conjugated diene of at least five (5) carbon atoms, such as isoprene, and B is a block of a polymer of at least one conjugated diene, different from that used to polymerize the block I, of at least four (4) carbon atoms, such as 1,3-butadiene. The B block is selectively hydrogenated, while each of the I blocks is unhydrogenated and therefore retains a sufficient amount of its original unsaturation to vulcanize the copolymer. There is also disclosed an alternative linear block copolymer containing at least one triblock of the first polymer block made from a minor proportion of at least one aryl-substituted olefin, such as styrene, and a major proportion of at least one conjugated diene used to polymerize the block I, the second middle polymer block of at least one diene used to polymerize the block B, and the third polymer block which is the same as the first polymer block.

Abstract: An ultra high molecular weight copolymer compositions of 1,3-conjugated dienes and aromatic vinyl compounds having a weight average molecular weight of greater than about 1,000,000 are described. The ultra high molecular weight copolymer compositions which are also characterized as having an intrinsic viscosity in tetrahydrofuran of at least about 4.0 may be obtained by a process which comprises polymerizing a 1,3-conjugated diene and a vinyl aromatic compound in a hydrocarbon solvent in the presence of a trimetalated 1-alkyne catalyst which comprises the reaction product of a 1-alkyne containing at least 4 carbon atoms, an organo metallic compound R.degree.M and 1,3-conjugated diene wherein R.degree. is a hydrocarbyl group, M is an alkali metal, the mole ratio of R.degree.M to 1-alkyne is about 3:1 and the mole ratio of conjugated diene to 1-alkyne is from about 2:1 to about 30:1.

Abstract: A method for preparing a diene polymer or copolymer having increased amounts of 1,2-microstructure is provided. The method involves polymerizing a diene monomer or mixture of a diene monomer and a vinyl aromatic hydrocarbon monomer in a hydrocarbon solvent in the presence of a catalytically effective amount of a catalyst composition comprising: (a) an organolithium initiator and (b) an oxolanyl cyclic acetal having the structural formula: ##STR1## wherein R is selected from the group consisting of hydrogen and alkyl groups containing from 1 to 4 carbon atoms and X is 0 or 1.

Abstract: Processes for the preparation of polymers which comprises a suspension free radical polymerization of a monomer phase comprised of at least two monomers, and a polymerization initiator; and an aqueous phase comprised of water and magnetite.

Abstract: A process for producing a high trans low vinyl conjugated diene (co)polymer, comprising polymerizing at least one conjugated diene alone or in combination with at least one alkenyl compound using a catalyst composition comprising (a) a barium compound, (b) an organoaluminum compound, (c) an organolithium compound and (d) a hydroxyl group-containing organic compound. This process enables the easy production of a high trans low vinyl conjugated diene (co)polymer having a high trans 1,4 bond content, a low vinyl bond content and a high molecular weight, at a high polymerization activity.

Abstract: Multifunctional cyclobutarene peroxide polymerization initiators comprising at least one cyclobutarene moiety linked through the aromatic ring to at least one peroxide containing group which catalyze free radical plymerizations, as well as participate in cyclobutarene initiated ring opening polymerizations. The cyclobutarene peroxides of this invention are useful for the production of cross-linked, branched and graft polymeric compositions.

Abstract: Compounds of formula I ##STR1## wherein n is 0 to 3, R.sub.1 and R.sub.2 are C.sub.1 -C.sub.12 alkyl, C.sub.5 -C.sub.8 cycloalkyl or --CH.sub.2 SR.sub.3, R.sub.3 is C.sub.1 -C.sub.18 alkyl, phenyl or benzyl, and R.sub.4 is hydrogen or CH.sub.3, are admirably suitable as chain-terminators in the anionic solution polymerisation of 1,3-dienes.

Abstract: The present invention provides a method for the polymerization or copolymerization of a monomer or blend of monomers selected from the group consisting of C-10 terpenes, vinyl aromatics and C-5 dienes that comprises complexing a Lewis acid with an organic ketone to produce a catalyst complex. The monomer or blend of monomers is added to the catalyst complex producing the reaction mixture. The reaction mixture is maintained at a temperature of between 10.degree. C. and 60.degree. C. and, when the reaction is complete, is quenched with water. The polymerized or copolymerized resin is then recovered.

Abstract: A process for the preparation of polymers which comprises forming an aqueous phase comprised of water and a surfactant; adding to the aqueous phase monomers; subsequently initiating polymerization of the monomers; thereafter adding a stabilizing component; and completing the polymerization.

Abstract: Multifunctional cyclobutarene peroxide polymerization initiators comprising at least one cyclobutarene moiety linked through the aromatic ring to at least one peroxide containing group which catalyze free radical polymerizations, as well as participate in cyclobutarene initiated ring opening polymerizations. The cyclobutarene peroxides of this invention are useful for the production of cross-linked, branched and graft polymeric compositions.

Abstract: A rubber composition is disclosed which contains not less than 20% by weight in a rubber component of a block copolymer composed of polymer or copolymer block units (A) and a random copolymer block units (B). The polymer or copolymer block units (A) are obtained by singly polymerizing a conjugated diolefine or copolymerizing the conjugated diolefine and a monovinyl aromatic hydrocarbon with use of a lithium initiator and contains not more than 10% by weight of the bound monovinyl aromatic hydrocarbon. The random copolymer block unit (B) are obtained by copolymerizing the conjugated diolefine and the monovinyl aromatic hydrocarbon and contain 15 to 80% by weight of the bound monovinyl aromatic hydrocarbon.

Abstract: A highly active anionic polymerization catalyst prepares butadiene polymers having a high 1,4-trans-dienyl content, the catalyst containing an organolithium compound, a barium, strontium or calcium compound, and trialkylaluminum compounds having at least 13 carbon atoms per molecule.

Abstract: An optical material of a high refractive index is formed of a copolymer obtained by copolymerizing 3-40 wt. % of 4-isopropenylbiphenyl, 30-97 wt. % of a monofunctional aromatic monomer represented by the following formula (I) or (II) and 0-67 wt. % of another monomer copolymerizable with 4-isopropenylbiphenyl and the monofunctional aromatic monomer. ##STR1## wherein R means a hydrogen atom or methyl group, X denotes ##STR2## in which n stands for an integer of 0-3, Y is a halogen atom other than a fluorine atom, or a methyl, hydroxyl or methoxy group, and m stands for an integer of 0-3, with the proviso that Y may be different from each other when m is 2 or 3.

Abstract: Process for inhibiting and for stopping radical induced polymerizations which employs an aromatic hydroxy dithiocarboxylic acid or salt thereof as stopping agent for deactivating radicals, thereby precluding the formation of carcinogenic nitrosamines.

Abstract: Synthetic elastomers are typically made commercially by employing emulsion polymerization or solution polymerization techniques. In such solution polymerization techniques, it is desirable to operate at the highest solids content which is practical. As a general rule, it is not practical to prepare such rubbers by solution polymerization at solids contents of higher than about 20 percent. However, the subject invention reveals a technique for preparing such rubbers by high solids solution polymerization at extremely high solids contents. This technique offers substantial advantages associated with eliminating large quantities of organic solvents.

Abstract: Narrow molecular weight telechelic and/or block copolymers are prepared by anionic polymerization using an initiator composition comprising a multifunctional lithium initiator in combination with an organic diamine or triamine and optionally a metal alkoxide.

Abstract: The invention relates to telechelic polymers based on radically polymerized, ethylenically unsaturated monomers which are obtained by polymerization by means of thiuram disulfides and dithiocarbamates, which have one or several additional functional reactive groups in addition to the carbamate group. The invention furthermore relates to the manufacture of the said type of telechelic polymers and to the use thereof, for example, as reactive precursors in higher-polymer linear or cross-linked products, especially as components of aqueous solutions, emulsions, dispersions, and suspensions for the preparation of coatings.

Abstract: A process for neutralizing the terminated remnant of an alkali metal anionic polymerization initiator comprising contacting the remnant with an organic acid halide.

Abstract: There are disclosed copolymers of aromatic vinyl compounds, e.g., styrene, and conjugated diolefins, e.g., butadiene, possessing a differential content of the aromatic vinyl compound such that in at least one of the end portions of the copolymer the differential content shows a sharp and substantial increase in the direction of the outer extremity of the end portion. Preferred compolymers are styrene-butadiene copolymers having a vinyl content of at least 30%. In special embodiments, the copolymer have a styrene content changing in a portion of no more than 5% of the copolymer chain from a first value to a second value, the second value being at least 25 percentage points greater than the first value, and the portion is present within a 10% terminal portion of the copolymer. The copolymers are useful in the tread portions of tires as tires containing such copolymers in the tread composition have improved rolling resistance and/or grip on wet road surfaces.

Abstract: A catalyst composition for polymerizing a conjugated diene which comprises the following (a), (b) and (c) components:(a) an organolithium-aluminum compound represented by the formula:LiAlR.sup.1 R.sup.2 R.sup.3 R.sup.4(b) an organobarium-aluminum compound represented by the formula:Ba(AlR.sup.1 R.sup.2 R.sup.3 R.sup.4).sub.2 or Ba[AlR.sup.1 R.sup.2 R.sup.3 (OR.sup.4)].sub.2(c) a lithium alkoxide represented by the formula:LiOR.sup.5The conjugated diene polymer or copolymer obtained by polymerizing a conjugated diene alone or in combination with other monomer with the above catalyst composition in an inert organic solvent has a high trans-1,4 bond content, a low vinyl bond content and a low cis-1,4 bond content.

Abstract: Vinyl aromatic-conjugated diene copolymers having polymer chains which end with an alkali metal and which are obtained by the polymerization in solution of at least one vinyl aromatic hydrocarbon and of a conjugated diene in the presence of a catalyst based on an alkali metal are decolorized by treating the copolymer with a monocarboxylic acid of general formula(Y).sub.2-n --X--(R--COOH).sub.nin which X is S, S--CH.sub.2 --S, or S--S, and Y and R are alkyl radicals having 1 to 16 carbon atoms and n is 1 or 2.

Abstract: In the suspension polymerization of styrene monomers in water using suitable suspension stabilizers, the only modifier needed has been found to be organotin compounds in amounts from 10 to 1000 ppm based on monomer. The product beads have a narrow bead size distribution.

Abstract: There is disclosed copolymers of aromatic vinyl compounds, e.g., styrene, and conjugated diolefins, e.g., butadiene, possessing a differential content of the aromatic vinyl compound such that in at least one of the end portions of the copolymer the differential content shows a sharp and substantial increase in the direction of the outer extremity of the end portion. Preferred copolymers are styrene-butadiene copolymers having a vinyl content of at least 30%. In special embodiments, the copolymers have a styrene content changing in a portion of no more than 5% of the copolymer chain from a first value to a second value, the second value being at least 25 percentage points greater than the first value, and the portion is present within a 10% terminal portion of the copolymer. The copolymers are useful in the tread portions of tires as tires containing such copolymers in the tread composition have improved rolling resistance and/or grip on wet road surfaces.

Abstract: It has been determined that certain rubbery polymers having multiple glass transition temperatures can be utilized in making tires which have improved rolling resistance, improved wet skid resistance, and outstanding tread wear. These rubbery polymers are derived from at least one conjugated diolefin monomer, have a first glass transition temperature which is between -110.degree. C. and -20.degree. C. and have a second glass transition temperature which is between -50.degree. C. and 0.degree. C. These rubber polymers can be homopolymers of conjugated diolefin monomers, copolymers of more than one conjugated diolefin monomer, or copolymers derived from at least one conjugated diolefin monomer and at least one vinyl aromatic monomer.

Abstract: A composition for tires containing at least 30% star shaped random styrene-butadiene copolymer obtained by solution polymerization, having a styrene content of less than 20% and more than 10% and a vinyl content of less than 50% and more than 40%, the composition value X of said copolymers being in a range of 26 to 39 obtained by using the equation; ##EQU1## wherein BR is the butadiene component, the glass transition temperature being a single one below -50.degree. C. and lower than estimated glass transition temperature following Gordon-Taylor equation by 5.degree. to 10.degree. C. and a cured composition showing loss modulus of lower than 1.times.10.sup.-7 dyn/cm.sup.2 and a ratio of rolling resistance to wet grip being smaller than 0.82.

Abstract: A new class of resins is provided which are copolymers of monomers comprising p-acetoxystyrene and any of certain designated polyunsaturated comonomers, viz., (1) a polyunsaturated carboxylic acid such as an alkyl ester of a carboxylic acid containing a conjugated diene group, e.g., a dialkyl muconate or an alkyl sorbate, or an allyl ester of a monoethylenically unsaturated carboxylic acid, e.g., diallyl maleate; (2) a conjugated diene hydrocarbon such as 2,5-dimethyl-2,4-hexadiene; or (3) a halogen-substituted conjugated diene hydrocarbon. One or more additional monoethylenically or polyethylenically unsaturated monomers, e.g. styrene, may be used in the preparation of the copolymer. The preferred copolymers are of p-acetoxystyrene and dimethyl muconate or diethyl muconate. The copolymer may be selectively hydrolyzed to corresponding copolymers of p-vinylphenol.

Abstract: This invention provides an improvement in anionic polymerization processes which comprise both a batch polymerization step to form and partially grow living polymer chains and a subsequent continuous or semi-continuous step in which growth of the chains is continued. For purposes of this improvement, the transition to the continuous or semi-continuous step takes place before the molar concentration of monomer in the batch polymerization step is depleted to a level below that of the living chains. Anionic polymerization processes are recognized as particularly useful for the production of polymers having narrow molecular weight distributions. Practice under the invention is found to enhance the narrow distribution of the polymer product by controlling thermal die-out of chains which has occurred in conventional processes during the transition from batch to continuous or semi-continuous polymerization steps.

Abstract: Coupling agents suitable to be synthetized by cyclo-oligomerization of 3-methylbutyn-1-ol-3 with subsequent dehydration of the alcohol compounds, and their use in a method for the termination of living polymers obtained by means of the anionic polymerization of diene and/or vinylaromatic monomers.

Abstract: A rubber composition for a tire tread comprising a novel modified styrene-butadiene copolymer rubber, carbon black, and aromatic oil.

Abstract: A tire whose tread comprises as elastomer a styrene-butadiene or a styrene-isoprene co-polymer having a glass transition temperature above minus 50.degree. C., said composition having a rebound resilience of 55% or more.The glass transition temperature is preferably between minus 40.degree. C. and minus 25.degree. C. and the rebound resilience is preferably between 60% and 70%.

Abstract: Disclosed is a diene elastomer composition especially suitable as tread rubber of tires which has low rolling resistance and high wet grip in combination. This elastomer composition contains a rubber material comprising an elastomeric polymer component of a butadiene polymer and/or a styrene-butadiene copolymer and a rubbery component. The elastomeric polymer is produced by using an organolithium compound as a polymerization initiator, and has a long chain end concentration (LCEC) of 1.5 or less as defined by the following formula: ##EQU1## wherein .alpha.: total number of terminal groups in long chain molecules per polymer,MW: a value obtained from intrinsic viscosity of the polymer as measured in toluene at 30.degree. C. by the following formulas:MW=70,660 x[.eta.].sup.1.282 for styrene-butadiene copolymer,MW=79,167 x[.eta.].sup.1.443 for butadiene polymer,.beta.i: weight fraction of component i when MW=(MW).sub.i.