A modified conjugated diene-based polymer containing: having a weight average molecular weight of 20×10.sup.4 or more and 300×10.sup.4 or less, having a star-branched structure with a conjugated diene-based polymer chain bonded to a modifier residue, wherein the modifier residue has at least 4 silicon atoms, and alkoxy groups and/or hydroxyl groups and the conjugated diene-based polymer chain is bonded to the silicon atom, wherein the number of alkoxy groups and/or hydroxyl groups in the modifier residue is larger than the number of the silicon atoms on average.

Provided is novel polybutadiene having high isotacticity. The polybutadiene has a triad isotacticity (mm) of 72% or more.

[Problem to be Solved] Provided is a method for producing a non-petrochemical-derived conjugated diene polymer using an alcohol derived from a non-petrochemical raw material.

[Means to Solve the Problem] In the present invention, the method is characterized in that a non-petrochemical-derived conjugated diene polymer is produced using an alcohol derived from a non-petrochemical raw material having an iron content of 0.0001 mg/L to 2 mg/L.

The present invention is directed to a rubber composition comprising 80 phr to 100 phr of at least one solution polymerized styrene-butadiene rubber, 0 phr to 20 phr of at least one polybutadiene, 55 phr to 200 phr of a filler, at least 15 phr of oil, wherein the filler to oil ratio by weight is between 3.5:1 and 8.0:1, and wherein the weight average molecular weight (Mw) of the at least one solution polymerized styrene-butadiene rubber is within a range of 400,000 to 1,000,000 g/mol. Moreover, the present invention is directed to a tire comprising such a rubber composition.

The bead portion (60) of the pneumatic tire (10) includes a bead structure (61) having a bead core (62) in which a bead cord (62a) formed of a metal material is covered with a resin material, and a film-like member (64) covering the periphery of the bead structure (61). The film-like member (64) is formed of a material having a lower moisture permeability than the resin material.

The bead portion of a pneumatic tire has a bead structure including a bead core having a bead cord covered with a resin material, and a bead filler continuous to the bead core and formed of the resin material and tapered outside in the tire radial direction. The bead structure has a weld line of the resin material. The weld line is formed inside in the tire radial direction more than ⅔ of the total height along the tire radial direction of the bead structure.

The invention is directed to a vulcanizable rubber composition comprising, based on parts by weight per 100 parts by weight elastomer (phr):100 phr of at least one diene-based elastomer; from 1-80 phr of carbon black; from 0 to 100 phr of silica; from 1 to 10 phr of a surface-functionalized carbon allotrope; from 1 to 20 parts by weight of a sulfur-containing organosilane per 100 parts by weight of the silica; and from 0.1 to 10 phr of a tetrazine compound of formula 1

##STR00001##

where X.sup.1 and X.sup.2 each represent a heterocyclic group. The invention also includes a pneumatic tire comprising the vulcanizable rubber composition.

A rubber-steel cord composite according to an embodiment is formed by vulcanizing and bonding a rubber composition containing 1 to 10 parts by mass of sulfur, 0.1 to 5 parts by mass of N,N-dibenzylbenzothiazole-2-sulfenamide, and 0.1 to 5 parts by mass of either one or both of hexamethylene bis-thiosulfate disodium salt dihydrate and 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane, with respect to 100 parts by mass of diene rubber containing natural rubber, and a steel cord. A pneumatic tire according to an embodiment includes the rubber-steel cord composite.

The present disclosure provides a novel and practical alcohol and derivatives thereof which have more industrial value than existing petrochemical raw materials. The present disclosure further provides ethanol, characterized in that a peak in gas chromatography measured by gas chromatograph mass spectrometry (GC/MS) has at least one peak with a retention time selected from (A) a peak of 5 minutes 25 seconds to 5 minutes 35 seconds and two peaks of 2 minutes 55 seconds to 3 minutes 5 seconds; (B) a peak of 12 minutes 30 seconds to 12 minutes 40 seconds; (C) a peak of 6 minutes 36 seconds to 6 minutes 45 seconds; and (D) a peak of 15 minutes 00 seconds to 15 minutes 15 seconds.

This invention is based upon the discovery that benzoxazine resins can be incorporated into certain rubber compositions to increase the stiffness thereof without increasing hysteresis or reducing tear strength. Such benzoxazine resin reinforced rubber formulations can accordingly be used beneficially in components of rubber products where high stiffness is desirable. Since these benzoxazine resin reinforced rubbers do not increase levels of hysteresis, they can be used in tires components, such as apexes, chaffers, and high stiffness tread blocks without compromising fuel efficiency. This invention more specifically reveals a radial tire having an apex, a chaffer, or a hard tread block segment which is comprised of a rubbery polymer and a benzoxazine resin.