Abstract: A curing low dielectric loss tangent film using a low dielectric loss tangent composition containing a polyfunctional styrene compound having excellent dielectric characteristics, and a wiring film using the same as an insulating layer are provided. The low dielectric loss tangent film contains a high molecular weight material and a crosslinking ingredient with a weight average molecular weight of 1000 or less having a plurality of styrene groups shown by the following general formula: (where R represents a hydrocarbon skeleton, R1, which may be identical or different with each other, represents a hydrogen atom or a hydrocarbon group of 1 to 20 carbon atoms, R2, R3 and R4, which may be identical or different with each other, each represents a hydrogen atom or an alkyl group of 1 to 6 carbon atoms, m represents an integer of 1 to 4, and n represents an integer of 2 or greater).

Abstract: The present invention relates to substantially free-flowing polymer particles. The polymer particles are those which have a one millimeter penetration temperature of less than about 75° C. as determined by thermal mechanical analysis or an unconfined yield strength of greater than about 15 pounds per square foot (73 kilograms per square meter). The composition also comprises an effective amount of an anti-blocking agent in the presence or absence of a binding agent.

Abstract: This invention relates to a resin composition useful as a vibration-damping agent and the like. The resin composition is formulated by adding 1 wt % or more of styrenated phenol obtained by the reaction of a phenol with styrene to a polycyclic aromatic oligomer obtained by condensing a polycyclic aromatic compound containing 2 to 3 rings and formaldehyde. The polycyclic aromatic oligomer is obtained by the reaction of a polycyclic aromatic compound with formaldehyde and, if necessary, further with a phenol in the presence of an acid catalyst and has a number average molecular weight of 300–1000. The styrenated phenol is obtained by the reaction of 1 mole of a phenol with 1–2.5 moles of styrene in the presence of an acid catalyst.

Abstract: A composition of matter and a solvent system for use in providing a water resistant coating to basement walls is disclosed. The solvent system comprises a chlorinated solvent blend. The solvent system and coating composition have no flash point, are non-flammable and provide an improved consistent coating when applied to walls.

Abstract: The present invention relates to a shaped article containing at least one peroxide curable compound containing a butyl-like polymer(s) without any conjugated aliphatic diene in its composition, said polymer containing less than 15 wt. % of solid matter insoluble in boiling cyclohexane under reflux for 60 min. The present invention also relates to a sealing material and a medical device containing at least one peroxide-curable compound containing a butyl-like polymer containing less than 15 wt. % of solid matter insoluble in boiling cyclohexane under reflux for 60 min. Further, the present invention relates to a process for producing a butyl-like polymer having no conjugated aliphatic diene in its composition and containing less than 15 wt. % of solid matter insoluble in boiling cyclohexane under reflux for 60 min.

Abstract: The present invention reveals a tire having a tread that is comprised of (1) 30 phr to 80 phr of a non-random styrene-butadiene rubber comprised of polymer chains that are derived from styrene and 1,3-butadiene, wherein from about 10 weight percent to about 50 weight percent of the repeat units in the styrene-butadiene rubber are derived from styrene, wherein from about 60 weight percent to about 90 weight percent of the repeat units in the styrene-butadiene rubber are derived from 1,3-butadiene, wherein from about 30 weight percent to about 50 weight percent of the styrene repeat units are in sequences containing 5 to 20 styrene repeat units, wherein the bound styrene content found in the first half of the polymer chains differs from the bound styrene content found in the second half of the polymer chains by at least 5 weight percent, wherein the styrene-butadiene rubber has a 1,2-vinyl content which is within the range of about 8 percent to about 20 percent, wherein the styrene-butadiene rubber has a number

Abstract: A catalyst paste composition for making electrodes has a uniform dispersion condition of a carbon black supporting a hydrogen reduction catalyst and is excellent in storage stability. The catalyst paste composition comprises a carbon black supporting a hydrogen reduction catalyst, an electrolyte, a water-soluble sulfonated polymer and a solvent.

Abstract: There is disclosed a fire-retardant resin composition, which comprises: a thermoplastic resin component (A) comprising (a) a block copolymer mainly made of a vinyl aromatic compound and a conjugated diene compound as its constitutional components, and/or a hydrogenated block copolymer of the block copolymer, (b) a nonaromatic-series softener for rubber, (c) an ethylene/?-olefin copolymer, and (d) a polypropylene resin; and (e) an organic peroxide, (f) a (meth)acrylate-series and/or allyl-series crosslinking aid, and a metal hydrate (B), wherein a specific amount of the metal hydrate (B) to be used is a metal hydrate being pretreated with a silane coupling agent, and the fire-retardant resin composition is a mixture of the above formulation that is heated and kneaded at a temperature equal to or higher than the melting temperature of the (A). There is also disclosed a wiring material and other molded parts, in which the resin composition is utilized.

Abstract: An oil-extended rubber comprising a conjugated diene rubber having a specific amount of isoprene units, and an extender oil incorporated therein, characterized in that the rubber is obtained by polymerizing a monomer mixture comprising 1,3-butadiene and an aromatic vinyl monomer with the aid of an organic active metal as an initiator in a hydrocarbon medium; subsequently adding isoprene to continue polymerization, then; reacting the resulting polymer having an activated terminal with a coupling agent. A rubber composition comprising the oil-extended rubber is suitable for tread of tire having a low fuel consumption.

Abstract: This invention relates to a process for producing a free radical control agent of the structural formula: wherein Z is selected from the group consisting of wherein R1 is an alkyl group of 1 to 4 carbon atoms, cyclohexyl or phenyl; wherein R2 is an alkoxy group of 1 to 8 carbon atoms or a cycloalkoxy group of 5 to 8 carbon atoms; wherein Alk is a divalent hydrocarbon of 1 to 18 carbon atoms; and wherein Y represents a functional group that is capable of activating a vinylic carbon toward free radical addition; said process comprising the steps of (1) reacting a mercaptosilane of the structural formula: Z-Alk-SH with carbon disulfide in the presence of a phase transfer catalyst and an alkali metal hydroxide to produce a trithiocarbonate salt; and (2) reacting the trithiocarbonate salt with a halogen containing compound of the structural formula X-Y to produce the free radical control agent, wherein X represents a halogen atom.

Abstract: A diene rubber (A) having a weight average molecular weight (Mw) of 100,000 to 3,000,000, an Mw/number average molecular weight (Mn) ratio of 1.30 to 2.50, and an Mw/peak top molecular weight (Mp) ratio 0.70 to 1.30. A rubber composition comprising the diene rubber (A) and a diene rubber (B) having an Mw of 2,000 to 90,0000 and/or an oil extender for rubber has good processability and can give a rubber vulcanizate having high tensile strength and good abrasion resistance. The diene rubber (A) is produced by conducting a living polymerization of diene monomer in a hydrocarbon solvent; adding a polymerization stopper to a polymerization mixture at a conversion of 5 to 98% to deactivate 10 to 90% by mole of active terminals present as of the initiation of polymerization; and finally adding a polymerization stopper to completely terminate the polymerization reaction.

Abstract: The invention is directed to an oil extended rubber and composition comprising: a solution-polymerized elastomer derived from at least one conjugated diene monomer and at least one vinyl aromatic monomer, the elastomer coupled with at least one metal selected from the group consisting of silicon and tin; and from about 5 to about 70 parts by weight, per 100 parts by weight of elastomer (phr), of a process oil having a glass transition temperature of from about ?80° C. to about ?40° C., a polycyclic aromatic content of less than 3 percent by weight as determined by the IP346 method, and an aromatic content of less than 20 percent by weight as measured by ASTM D2140.

Abstract: The invention is directed to an oil extended rubber and composition comprising: a solution polymerized elastomer derived from isoprene and optionally at least member of the group consisting of conjugated dienes and vinyl aromatic monomers; and from about 5 to about 70 parts by weight, per 100 parts by weight of elastomer (phr), of a process oil having a glass transition temperature of from about ?80° C. to about ?40° C. and a polycyclic aromatic content of less than 3 percent by weight as determined by the IP346 method.

Abstract: Gypsum wallboard compositions are disclosed which contain functionalized styrene butadiene latex polymers. Methods for the use of the compositions in the manufacture of wallboard panels and sheets is presented.

Abstract: An external plaster using an aqueous hot melted type adhesive base material stably containing water-soluble drug having good drug releasability, so that bioavailability of the drug is enhanced, is provided. The aqueous hot melted type adhesive base material used in the external plaster comprising as essential components a styrene-isoprene-styrene block copolymer, an adhesive resin, an antioxidant, lanolin, and water.

Abstract: This invention provides a rubber composition comprising: a softening agent including a hydrogenated naphthenic oil of which an extract quantity of dimethylsulfoxide (DMSO) by IP 346 method is controlled to less than 3% by weight and blending at least one selected from a group of (1) a styrene-butadiene copolymer rubber with a bond styrene quantity in molecular of from 10% by weight to 60% by weight and with a vinyl bond quantity of the butadiene part of from 10% to 80% and (2) a butadiene rubber with a cis bond quantity of at least 30%. The rubber composition is superior in fracture characteristics, loss characteristic and wear resistance, and it is applicable to various rubber products, a pneumatic tire and, in particular, a tire tread.

Abstract: An uncured epoxy adhesive comprising a resin component, a hardener component, and a microencapsulated accelerator component. The microencapsulated accelerator component comprises an infrared absorber, an accelerator and a wall that covers substantially the entire surface of the accelerator. The epoxy adhesive is cured by exposing it to infrared energy. The infrared energy is absorbed by the infrared absorber which disintegrates the wall and allows the accelerator to come into contact with the other adhesive components and initiate the curing polymerization reaction.

Abstract: Gypsum wallboard compositions are disclosed which contain functionalized styrene butadiene latex polymers. Methods for the use of the compositions in the manufacture of wallboard panels and sheets is presented.

Abstract: Disclosed is a chipping resistance-imparting aqueous dispersion composition comprising a nonvolatile component (film-forming component) dispersed in water, said nonvolatile component containing an olefin thermoplastic elastomer or a styrene/conjugated diene block copolymer or its hydrogenation product. A coating film obtained by the use of the aqueous dispersion composition as an aqueous primer or an additive to a water paint is excellent in chipping resistance as well as in other properties such as film appearance, adhesion properties, heat resistance, moisture resistance and gasoline resistance.

Abstract: This invention relates to a carbon black modified by a two step process in which carbon black is initially treated with functional monomers by an electropolymerization process to form a functionalized carbon black having an initial polymer attached to, of grafted to, the carbon black following which (A) at least one diene monomer, or (B) living anionic catalysis prepared polymer, is introduced to the functionalized carbon black to continue the polymerization, starting from a living end of the initially formed polymer, and thereby form an extended diene-based polymer. By the addition of the diene monomer or the live anionic polymer to form the associated extended diene-based polymer, it is contemplated that the modified carbon black is rendered more compatible with diene-based elastomers. Such modified carbon black may be used, for example, as reinforcement for component(s) of various articles of manufacture, including tires.

Abstract: A readily water-redispersible and water-wettable polymer powder is prepared by spray-drying of an aqueous dispersion of polymer particles with admixing of a hydrophilic and of a hydrophobic antiblocking agent.

Abstract: Cushions and cushion elements with non-intersecting-columnar elastomeric members exhibiting compression instability are disclosed. The cushions and cushion elements may be made from gelatinous elastomer materials. The cushions and cushion elements have application in a variety of fields, including foot care products, seat cushions, mattresses and mattress overlays for consumer and medical applications, carry straps, sports injury prevention, orthopedics, vibration dampeners for electrical and electronic equipment, shock absorbers and others.

Abstract: A semiconductor device wherein a resin containing as a cross-linking component a compound having a plurality of styrene group and represented by chemical formula [1] is used as an insulating material: where R is a hydrocarbon structure which may have a substituent group or groups, R1 is hydrogen, methyl, or ethyl, m is and integer of 1 to 4, and n is an integer of not less than 2. With this, a semiconductor device and a semiconductor package which show excellent transmission characteristics and less power consumption are provided.

Abstract: This invention relates to an UV stabilizing additive composition comprising an ortho-hydroxy triazine compound, a hindered hydroxybenzoate compound and optionally a hindered amine compound. This additive composition may be used to stabilize materials from UV radiation. This invention also contemplates a method of stabilizing a material by contacting the material with the UV stabilizing additive composition.

Abstract: The present invention relates to aqueous coating compositions containing A) at least one aqueous emulsion polymer, B) one or more polymer dispersions as a dispersion medium, C) at least one pigment, D) optionally a neutralizing agent and E) optionally a coatings additive. The present invention also relates to a process for preparing these aqueous coating compositions by preparing a dispersion paste by mixing components B), C) and D) with some of component E) and then component A) and the remainder of component E) are homogeneously blended with the dispersion paste. The present invention further relates to peelable coatings prepared from these coating compositions for the temporary protection of surfaces.

Abstract: An improved block paving sand comprising kiln dried sand mixed with a water-soluble polymer. The block paving sand is filled into gaps between blocks and then water is applied thereto. Upon contact with the water, the polymer coats the sand and then sets hard, thereby stabilising the block paving.

Abstract: The disclosure relates to a process for improving the processability, storage stability and/or cure rate of an uncured silica reinforced rubber composition where silica comprises the major filler in the reinforced rubber composition, which comprises combining a mixture comprising, rubber, silica and at least one organic compound having a low molecular weight and a functional group wherein said functional group is at least an epoxy group, such as an epoxy/ether, epoxy/hydroxyl, epoxy/ester, epoxy/amine, ether/amine, episulfide, episulfide/ether, episulfide/hydroxyl, episulfide/ester functional group located in a terminal or sterically unhindered position in the molecule of said organic compound where the molecular weight of said organic compound having a low molecular weight is less than 7,000, or the organic compound comprises an abietyl, styrenated resorcinol formaldehyde, or ester hydroxyl organic compound having a hydroxyl, ester, and optionally, an ether group, such as an ester diol.

Abstract: Modified silica fillers are prepared by contacting silica with blends or mixtures containing diorganodihalosilanes and tetrahalosilanes in weight ratios of 1:0.1 to 1:2, respectively. While dialkyldichlorosilanes and tetrahalosilanes such as dimethyldichlorosilane and silicon tetrachloride, respectively, are most preferred, the blends or mixtures may also comprise compositions containing other silanes such as mercaptopropyltriethoxysilane.

Abstract: Pneumatic rubber tire having at least one component or a rubber composition comprised of a major portion of relatively low Tg high cis 1,4-polybutadiene elastomer (BR) and a minor portion of a relatively high Tg, styrene-rich, styrene/isoprene elastomer (SIR) wherein the Tg of said BR is at least 60° C. lower than the Tg of said SIR. Said SIR has a styrene content of at least 30 weight percent. The styrene based units of said SIR are present substantially without large blocks of styrene units. Said BR is a high cis 1,4-polybutadiene having a cis 1,4-content of at least 96 percent and preferably has a branched macrostructure. In one aspect of the invention, said tire component is a tire tread, particularly a circumferential tire tread.

Abstract: The present invention provides an adhesive composition containing a block copolymer, wherein the block copolymer has a polymer block (A) which is principally composed of a &agr;-methyl styrene unit, and a polymer block (B) which is principally composed of a conjugated diene unit and of which at least part of carbon-carbon unsaturated double bonds may be hydrogenated, and having a good holding power at high temperatures.

Abstract: This invention relates to preparation and use of a rubber/carbon black composite comprised of at least one elastomer which contains a dispersion therein of carbon black aggregates. Such carbon black is formed by preparing a pre-blend comprised of uncompacted carbon black aggregates and oil and/or aqueous latex of, preferably, a low molecular weight diene-based elastomer particles, followed by blending said pre-blend with an aqueous emulsion of diene-based elastomer particles and/or with an organic solution of a diene-based elastomer, and/or with solid diene-based elastomers, and recovery therefrom of a solid rubber/carbon black composite comprised of said diene-based elastomer, (which may include butyl rubber, EPDM rubber and thermoplastic polymers), which contains a dispersion therein of said carbon black aggregates having an apparent density significantly lower than the specific gravity of said carbon black aggregates and significantly lower than compacted carbon black aggregates.

Abstract: An improved gelatinous elastomer is disclosed which uses an A-B-A triblock copolymer having a molecular weight in the range of 125,000 to 175,000, or about 150,000, and a plasticizer.

Abstract: A coupler is described for use in carbon black filled rubber compositions. The coupler includes an amine group and a thiol group or a polysulfidic linkage. The coupler improves the interaction of the carbon black with the rubber as measured by a decrease in the tan delta at 60° C. while substantially maintaining the tan delta at 0° C.

Abstract: Gypsum wallboard made lighter and less dense, without sacrificing strength, by adding to the gypsum slurry used in making the board a styrene butadiene polymer latex substantially stable against divalent ions in which the styrene butadiene polymer latex substantially stable against divalent ions in which the styrene butadiene polymer includes at least 0.25 wt. % of an ionic monomer.

Abstract: According to the present invention, there is provided a low dielectric loss tangent resin composition containing a crosslinking component having a weight average molecular weight of not more than 1,000 and a plurality of styrene groups and represented by the formula [1], wherein R is a hydrocarbon skeleton which may have a substituent, R1 is hydrogen, methyl or ethyl, m is an integer of 1-4 and n is an integer of 2 or more, and further containing at least one member selected from a high polymer having a weight average molecular weight of not less than 5,000 and a filler, which resin composition can give a cured product having a good flexibility, high tensile strength and low dielectric constant and dielectric loss tangent.

Abstract: Gel and gel composites health care articles, including masks, pads, blood bags, tubings, male and female tubing connectors, and needle protector sheath.

Abstract: Provided is a natural rubber obtained by drying a gathered natural rubber latex without coagulating, wherein a drum dryer and/or a conveyor type dryer are used for drying.

Abstract: The invention relates to a process for preparing nondusting free-flowing pigment concentrates with removal of the water from pigment suspensions comprising polymers and dispersants in a fluidized bed drier. The resulting bead-form pigment concentrates are nondusting and readily free-flowing. The invention further embraces the use of pigment concentrates prepared in this way for coloring plastics and polymers.

Abstract: The disclosure relates to a process for improving the processability, storage stability and/or cure rate of an uncured silica reinforced rubber composition where silica comprises the major filler in the reinforced rubber composition, which comprises combining a mixture comprising, rubber, silica and at least one organic compound having a low molecular weight and a functional group wherein said functional group is at least an epoxy group, such as an epoxy/ether, epoxy/hydroxyl, epoxy/ester, epoxy/amine, ether/amine, episulfide, episulfide/ether, episulfide/hydroxyl, episulfide/ester functional group located in a terminal or sterically unhindered position in the molecule of said organic compound where the molecular weight of said organic compound having a low molecular weight is less than 7,000, or the organic compound comprises an abietyl, styrenated resorcinol formaldehyde, or ester hydroxyl organic compound having a hydroxyl, ester, and optionally, an ether group, such as an ester diol.

Abstract: The present invention is a method of incorporating a water insoluble organic chemical into a styrene-butadiene rubber latex dispersion and the resulting styrene-butadiene rubber latex dispersion. A styrene-butadiene rubber latex dispersion is provided comprising an aqueous phase and a disperse phase, with the disperse phase including particles of styrene-butadiene rubber. An organic solvent that is miscible in water and the water insoluble organic chemical are added together to the styrene-butadiene rubber latex dispersion. The addition of the water-miscible organic solvent allows the water insoluble organic chemical to pass from the aqueous phase into the disperse phase thus limiting separation of the water insoluble organic chemical from the latex dispersion. The resulting SBR latex has increased properties over conventional latices that use the same amount of the water insoluble organic chemical but that do not include the water-miscible organic solvent.

Abstract: An objective of the invention is to provide a conjugated diene-based rubber having a specific composition and an oil extended rubber using the same, as well as a rubber composition capable of being converted into a vulcanized rubber which has a low rolling resistance, an excellent wearing resistance and the like, and is useful for a tire or the like. A conjugated diene-based rubber in the invention has repeating units consisting of 1 to 30% by mass of an olefinically unsaturated nitrile monomer unit such as acrylonitrile, 10 to 50% by mass of an aromatic vinyl monomer unit such as styrene, 19.9 to 88.9% by mass of a conjugated diene monomer unit such as 1,3-butadiene and 0.1 to 10% by mass of a monomer unit having one polymerizable unsaturated group and at least one functional group selected from the group consisting of an amino group, a hydroxyl group, an epoxy group, a carboxyl group and an alkoxysilyl group, and has a specific glass transition point and a Mooney viscosity [ML1+4(100° C.

Abstract: The present invention provides block copolymers which have reduced solvent sensitivity and which overcome the foregoing disadvantages. In one embodiment of the present invention, there is provided an asymmetric block copolymer of the structure A-B-C-A wherein each A block is formed of a vinyl aromatic hydrocarbon, preferably styrene, and has a weight average molecular weight of 5,000 to 50,000. B is a polybutadiene block having a weight average molecular weight of 1,000 to 15,000 and a vinyl content of less than 25% by weight, and C is an elastomeric conjugated diene polymer block having a weight average molecular weight of 25,000 to 200,000 and has a vinyl content of 30 to 90%, preferably 35 to 80%, and most preferably 35 to 70% by weight. In the second embodiment of the present invention, there is provided a hydrogenated block copolymer of the formula A-B-C-B-A wherein A, B, and C have the definitions set forth above.

Abstract: The present invention relates to a process for hydrogenating ethylenically unsaturated double bonds in polymers P by reacting an aqueous dispersion of at least one polymer P with hydrogen in the presence of at least one hydrogenation catalyst comprising at least one transition metal selected from rhodium and/or ruthenium and at least one nonionic phosphorus compound capable of forming a coordinative compound with the transition metal, which comprises incorporating the hydrogenation catalyst into the aqueous dispersion of the polymer P without adding a solvent. The present invention also relates to the aqueous dispersions of the hydrogenated polymers P obtainable by this process and to coating compositions comprising such dispersions.

Abstract: Self crosslinking aqueous polymer dispersions containing hard and soft copolymers containing polymerized units of a conjugated diene, a vinyl aromatic compound, an organic carboxylic acid and/or anhydride, and at least one crosslinker may be included in consolidated nonwoven constructions. The consolidated nonwoven construction is useful as a base material such as a bituminized roofing mat.

Abstract: A rubber composition comprised of an elastomer(s) reinforced with a particulate carbon black composite, and a coupling agent. Said carbon black composite contains integral silica on the surface thereof, wherein said carbon black composite is prepared by co-precipitating carbon black and silica from a dispersion of carbon black in sodium silicate to provide integral silica domains on the outer surface of the carbon black. Said carbon black composite is further functionalized by reacting it with a trialkoxy silane. A tire having a component comprised of such rubber composition, such as, for example, a tire tread is contemplated.

Abstract: One aspect of the invention is directed to a rubber composition which includes at least one sulfur-vulcanizable elastomer containing olefinic unsaturation, a first processing aid, and a second processing aid of the formula: wherein each of R1 and R2 independently is selected from the group consisting of alkyls having from 12 to 24 carbon atoms, and alkenyls having from 12 to 24 carbon atoms. The elastomer is present in an amount of 100 parts by weight. Also, the first processing aid may be present in an amount of 0 to 20 phr, and the second processing aid may be present in an amount of 0.2 to 20 phr. Another aspect of the invention is directed to a method of making the rubber composition described immediately above, with the method including the step of mixing the elastomer, first processing aid, and second processing aid.

Abstract: An elastomeric composition includes a single S-EB-S block copolymer having at least about 15 weight percent of styrene end blocks, wherein the weight average molecular weight of the styrene end blocks is at least about 7,000 Daltons and the weight average molecular weight of ethylene-butylene midblocks is at least about 60,000 Daltons, and a plasticizer in an amount sufficient to provide tactility in products made from the composition. To prepare articles such as medical film protective devices, the elastomeric composition is dissolved in a sufficient amount of a solvent to permit dip forming. A form having the shape of the desired product is dipped into the solution to build up a film of the elastomeric composition on the form. The dip-formed elastomeric films are free of pinholes and resistant to oxidative and ozone attack. The films are particularly suitable for use in products such as examination, surgical, and industrial gloves and condoms.

Abstract: A novel polymodal asymmetric elastomeric block copolymer and a pressure sensitive adhesive, tape and adhesive backed article made therefrom, such as a polymer foam article having a substantially smooth surface prepared by melt-mixing a polymer composition and a plurality of microspheres, at least one of which is an expandable polymeric microsphere, under process conditions, including temperature and shear rate, selected to form an expandable extrudable composition; and extruding the composition through a die.

Abstract: Mixture of at least one filler and organosilicon compounds of the general formula Y—Sx-Z, wherein the filler is surface-treated, hydrophobic, precipitated silica, are prepared by homogeneously applying an organosilicon compound from a nozzle to the surface-treated, hydrophobic, precipitated silica in a mixing unit at a temperature of less than 50° C. The mixture can be used in rubber mixtures.

Abstract: An oil-extended rubber comprising 100 weight parts of a rubber ingredient comprising a conjugated diene rubber wherein the ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) is in the range of 1.2 to 2.2, and the conjugated diene monomer units have a vinyl bond unit content of at least 20%, and 5-100 weight parts of a process oil having a total acid value of not larger than 1.0 mgKOH/g, a pour point of not higher than 50° C. and an aromatic carbon content of at least 20%. A rubber composition comprising 100 weight parts of the above-mentioned rubber ingredients, 5-100 weight parts of the process oil and 10-200 weight parts of a reinforcing agent. This rubber composition gives a crosslinked article having high tensile strength, high abrasion resistance and reduced heat build-up, and is useful, for example, as an automobile tire material.