The invention relates to a process for devulcanizing a vulcanized rubber mixture, comprising the following steps: A) providing or producing a vulcanized rubber mixture, B) comminuting the vulcanized rubber mixture to a granular material composed of vulcanized rubber particles, where the vulcanized rubber particles have a maximum particle diameter of 100 mm, C) extruding the vulcanized rubber particles produced in step B) in a twin-screw extruder at a shear rate of less than 100 s.sup.−1, where the temperature of the vulcanized rubber particles during extrusion is less than 200° C., to give a devulcanized rubber mixture having a temperature above 100° C., D) cooling the devulcanized rubber mixture in a further kneading unit, so as to give a devulcanized rubber mixture having a temperature in the range from 50° C. to 100° C. The invention further relates to an apparatus for performing the process and to the use of the apparatus for devulcanization of a vulcanized rubber mixture.

An object of the present invention is to provide novel crystals. Provided are crystals of 3-hydroxy-N′-(1,3-dimethylbutylidene)-2-naphthoic acid hydrazide having an X-ray powder diffraction pattern comprising a peak of maximum intensity at an angle of diffraction (2θ) of 6.1±0.2°.

An object of the present invention is to provide novel crystals. Provided are crystals of 3-hydroxy-N′-(1,3-dimethylbutylidene)-2-naphthoic acid hydrazide having an X-ray powder diffraction pattern comprising a peak of maximum intensity at an angle of diffraction (2θ) of 6.1±0.2°.

An adhesive for a tennis ball of the present disclosure includes base rubber and a filler. The base rubber contains, as a main component thereof, liquid rubber having a number average molecular weight of not less than 10,000. The filler has an average nitrogen specific surface area of not less than 40 m.sup.2/g. A tennis ball of the present disclosure includes a hollow core made of a rubber material. The core includes two hemispherical half cores. The two half cores are adhered to each other by using the adhesive for a tennis ball.

An adhesive for a tennis ball of the present disclosure includes base rubber and a filler. The base rubber contains, as a main component thereof, liquid rubber having a number average molecular weight of not less than 10,000. The filler has an average nitrogen specific surface area of not less than 40 m.sup.2/g. A tennis ball of the present disclosure includes a hollow core made of a rubber material. The core includes two hemispherical half cores. The two half cores are adhered to each other by using the adhesive for a tennis ball.

It is an object to provide a tire having well-improved fuel efficiency, wet grip performance, abrasion resistance, and wet grip performance at a later stage of abrasion. Provided is a tire comprising a tread part of a rubber composition comprising a rubber component comprising an isoprene-based rubber and a styrene-butadiene rubber, wherein a vinyl content of the styrene-butadiene rubber is greater than 26 mol %, wherein a given ratio A of an ash content of the rubber composition is greater than 25 mol %, wherein the tread part comprises two or more circumferential main grooves extending in a tire circumferential direction, and land parts partitioned by the circumferential main grooves, wherein at least one land part of the land parts comprises at least one given flask-like circumferential groove extending in the tire circumferential direction.

It is an object to provide a tire having well-improved fuel efficiency, wet grip performance, abrasion resistance, and wet grip performance at a later stage of abrasion. Provided is a tire comprising a tread part of a rubber composition comprising a rubber component comprising an isoprene-based rubber and a styrene-butadiene rubber, wherein a vinyl content of the styrene-butadiene rubber is greater than 26 mol %, wherein a given ratio A of an ash content of the rubber composition is greater than 25 mol %, wherein the tread part comprises two or more circumferential main grooves extending in a tire circumferential direction, and land parts partitioned by the circumferential main grooves, wherein at least one land part of the land parts comprises at least one given flask-like circumferential groove extending in the tire circumferential direction.

It is an object to provide a tire having well-improved fuel efficiency, wet grip performance, abrasion resistance, and wet grip performance at a later stage of abrasion. Provided is a tire comprising a tread part of a rubber composition comprising a rubber component comprising an isoprene-based rubber and a styrene-butadiene rubber, wherein a vinyl content of the styrene-butadiene rubber is greater than 26 mol %, wherein a given ratio A of an ash content of the rubber composition is greater than 25 mol %, wherein the tread part comprises two or more circumferential main grooves extending in a tire circumferential direction, and land parts partitioned by the circumferential main grooves, wherein at least one land part of the land parts comprises at least one given flask-like circumferential groove extending in the tire circumferential direction.

The present disclosure provides a tire in which cracks or other defects on the surface of a tire component can be reduced to provide an excellent market life. A tire including a rubber layer and satisfying the following relationships (1) and (2): E1/E2×100>25 (1); and E1/E2×T×100>50 (2) wherein E1 denotes the fracture energy (MPa.Math.%) determined by cutting a No. 7 dumbbell-shaped specimen cut out of the rubber layer, heat-treating the specimen with the cut sections attached to each other at 170° C. for 12 minutes, and then stretching and deforming the specimen; E2 denotes the fracture energy (MPa.Math.%) determined by heat-treating a No. 7 dumbbell-shaped specimen cut out of the rubber layer at 170° C. for 12 minutes and then stretching and deforming the specimen; and T denotes the thickness (mm) of the rubber layer.

The present disclosure provides a tire in which cracks or other defects on the surface of a tire component can be reduced to provide an excellent market life. A tire including a rubber layer and satisfying the following relationships (1) and (2): E1/E2×100>25 (1); and E1/E2×T×100>50 (2) wherein E1 denotes the fracture energy (MPa.Math.%) determined by cutting a No. 7 dumbbell-shaped specimen cut out of the rubber layer, heat-treating the specimen with the cut sections attached to each other at 170° C. for 12 minutes, and then stretching and deforming the specimen; E2 denotes the fracture energy (MPa.Math.%) determined by heat-treating a No. 7 dumbbell-shaped specimen cut out of the rubber layer at 170° C. for 12 minutes and then stretching and deforming the specimen; and T denotes the thickness (mm) of the rubber layer.