Cold flow-reduced polymers having good processing characteristics have, at the ends of the polymer chains, a silane-containing carboxyl group of the formula (I) ##STR00001##
where R.sup.1 and R.sup.2 are the same or different and are each an H, alkyl, alkoxy, cycloalkyl, cycloalkoxy, aryl, aryloxy, alkaryl, alkaryloxy, aralkyl or aralkoxy; R.sup.3 and R.sup.4 are the same or different and are each an H, alkyl, cycloalkyl, aryl, alkaryl or aralkyl radical; A is a divalent organic radical.

The present invention provides a rubber composition for tire treads, the rubber composition achieving high rubber hardness and 300% modulus at high temperatures, and excellent dry grip properties when formed into a tire, along with a pneumatic tire obtainable by using the same. The rubber composition for tire treads of the present invention contains carbon black and a diene rubber including a carboxy-modified polymer. The carbon black content is from 80 to 150 parts by mass per 100 parts by mass of the diene rubber. The carboxy-modified polymer is obtained by modifying styrene-butadiene rubber (A) with a nitrone compound having carboxy group (B), and the content of the carboxy-modified polymer in the diene rubber is from 10 to 100 mass %. The content of styrene units in styrene-butadiene rubber (A) is at least 36 mass %. The degree of modification of the carboxy-modified polymer is from 0.02 to 4.0 mol %.

The present invention provides a rubber composition for tire treads, the rubber composition achieving high rubber hardness and 300% modulus at high temperatures, and excellent dry grip properties when formed into a tire, along with a pneumatic tire obtainable by using the same. The rubber composition for tire treads of the present invention contains carbon black and a diene rubber including a carboxy-modified polymer. The carbon black content is from 80 to 150 parts by mass per 100 parts by mass of the diene rubber. The carboxy-modified polymer is obtained by modifying styrene-butadiene rubber (A) with a nitrone compound having carboxy group (B), and the content of the carboxy-modified polymer in the diene rubber is from 10 to 100 mass %. The content of styrene units in styrene-butadiene rubber (A) is at least 36 mass %. The degree of modification of the carboxy-modified polymer is from 0.02 to 4.0 mol %.

Polymers are functionalized at chain ends thereof with silane-containing carboxyl groups of the formula (I) ##STR00001##
where R.sup.1 and R.sup.2 are the same or different and are each an H, alkyl, alkoxy, cycloalkyl, cycloalkoxy, aryl, aryloxy, alkaryl, alkaryloxy, aralkyl or aralkoxy radical; R.sup.3 and R.sup.4 are the same or different and are each an H, alkyl, cycloalkyl, aryl, alkaryl or aralkyl radical; and A is a divalent organic radical.

Polymers are functionalized at chain ends thereof with silane-containing carboxyl groups of the formula (I) ##STR00001##
where R.sup.1 and R.sup.2 are the same or different and are each an H, alkyl, alkoxy, cycloalkyl, cycloalkoxy, aryl, aryloxy, alkaryl, alkaryloxy, aralkyl or aralkoxy radical; R.sup.3 and R.sup.4 are the same or different and are each an H, alkyl, cycloalkyl, aryl, alkaryl or aralkyl radical; and A is a divalent organic radical.

A nitrile group-containing copolymer rubber which has a hydroxyl group, carboxyl group, or carbon-carbon double bond at an end carbon atom or on a carbon atom which bonds with the end carbon atom is provided. The nitrile group-containing copolymer rubber is preferably obtained by a metathesis reaction. A nitrile group-containing copolymer rubber which is excellent in cross-linkability can be provided.

A nitrile group-containing copolymer rubber which has a hydroxyl group, carboxyl group, or carbon-carbon double bond at an end carbon atom or on a carbon atom which bonds with the end carbon atom is provided. The nitrile group-containing copolymer rubber is preferably obtained by a metathesis reaction. A nitrile group-containing copolymer rubber which is excellent in cross-linkability can be provided.

The present disclosure provides a rubber composition and a tire which can suppress changes in performances caused by changes in road conditions from dry to wet road surface or from wet to dry road surface. The tire of the present disclosure has E* when wet with water (MPa), E* when dry (MPa), tan when wet with water, tan when dry, 40% modulus (MPa) at 70 C. before a tensile test, and 40% modulus (MPa) at 70 C. after the tensile test which satisfy the following formulas (1) to (3): (1) E* when wet with water/E* when dry 0.90 (2) tan when wet with water/tan when dry >1.00 (3) 40% modulus at 70 C. after tensile test/40% modulus at 70 C. before tensile test 0.45 where E* and tan refer to a complex modulus of elasticity and a loss tangent, respectively, after 30 minutes from the start of measurement under the conditions of a temperature of 30 C., an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, an elongation mode, and a measurement duration of 30 minutes; 40% modulus at 70 C. after the tensile test refers to a tensile stress at an elongation of 40% determined after extension of 50% at 70 C., releasing the stress, and then measuring the tensile stress at an elongation of 40% at 70 C. in accordance with JIS K 6251:2010; and 40% modulus at 70 C. before a tensile test refers to a tensile stress at an elongation of 40% measured before the tensile test at 70 C. in accordance with JIS K 6251:2010.

The present disclosure provides a rubber composition and a tire which can suppress changes in performances caused by changes in road conditions from dry to wet road surface or from wet to dry road surface. The tire of the present disclosure has E* when wet with water (MPa), E* when dry (MPa), tan when wet with water, tan when dry, 40% modulus (MPa) at 70 C. before a tensile test, and 40% modulus (MPa) at 70 C. after the tensile test which satisfy the following formulas (1) to (3): (1) E* when wet with water/E* when dry 0.90 (2) tan when wet with water/tan when dry >1.00 (3) 40% modulus at 70 C. after tensile test/40% modulus at 70 C. before tensile test 0.45 where E* and tan refer to a complex modulus of elasticity and a loss tangent, respectively, after 30 minutes from the start of measurement under the conditions of a temperature of 30 C., an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, an elongation mode, and a measurement duration of 30 minutes; 40% modulus at 70 C. after the tensile test refers to a tensile stress at an elongation of 40% determined after extension of 50% at 70 C., releasing the stress, and then measuring the tensile stress at an elongation of 40% at 70 C. in accordance with JIS K 6251:2010; and 40% modulus at 70 C. before a tensile test refers to a tensile stress at an elongation of 40% measured before the tensile test at 70 C. in accordance with JIS K 6251:2010.

An aqueous polymer latex composition is described for the preparation of an elastomeric film comprising: (I) particles of a latex polymer obtained by free-radical emulsion polymerization of a mixture of ethylenically unsaturated monomers, the particles bearing functional groups (a); and (II) a cross-linking component selected from monomeric compounds and oligomeric or polymeric compounds that are not prepared be free-radical addition polymerization, the cross-linking component comprising functional groups (b) and (c) that are different from each other, wherein functional group (b) forms upon reaction with functional group (a) a thermally reversible linkage selected from one or more of (i) a linkage having the structural formula ##STR00001## wherein X, n, R1 and R2 are as defined; and (ii) a beta-hydroxy ester linkage; and functional groups (c) on different molecules of component (II) are capable of reacting with each other to provide elastomeric films having self-healing properties that can be repaired and recycled.