A process for manufacturing a rubber composition which comprises more than 50 phr of a diene elastomer rich in ethylene units, a reinforcing filler comprising a carbon black and a vulcanization system comprising sulfur, a sulfenamide as primary accelerator and a thiuram polysulfide or a mixture of a thiuram polysulfide and a guanidine as secondary accelerator is provided. The process comprises mixing the highly saturated diene elastomer, the reinforcing filler and the secondary accelerator by kneading at a temperature above 110′C, in the absence of the sulfur and the primary accelerator, and incorporating the sulfur and the primary accelerator into the rubber composition by kneading at a temperature below 110° C. The process makes it possible to reduce the hysteresis of the vulcanized rubber compositions.

A process for manufacturing a rubber composition which comprises more than 50 phr of a diene elastomer rich in ethylene units, a reinforcing filler comprising a carbon black and a vulcanization system comprising sulfur, a sulfenamide as primary accelerator and a thiuram polysulfide or a mixture of a thiuram polysulfide and a guanidine as secondary accelerator is provided. The process comprises mixing the highly saturated diene elastomer, the reinforcing filler and the secondary accelerator by kneading at a temperature above 110′C, in the absence of the sulfur and the primary accelerator, and incorporating the sulfur and the primary accelerator into the rubber composition by kneading at a temperature below 110° C. The process makes it possible to reduce the hysteresis of the vulcanized rubber compositions.

A process for manufacturing a rubber composition which comprises more than 50 phr of a diene elastomer rich in ethylene units, a reinforcing filler comprising a carbon black and a vulcanization system comprising sulfur, a sulfenamide as primary accelerator and a thiuram polysulfide or a mixture of a thiuram polysulfide and a guanidine as secondary accelerator is provided. The process comprises mixing the highly saturated diene elastomer, the reinforcing filler and the secondary accelerator by kneading at a temperature above 110′C, in the absence of the sulfur and the primary accelerator, and incorporating the sulfur and the primary accelerator into the rubber composition by kneading at a temperature below 110° C. The process makes it possible to reduce the hysteresis of the vulcanized rubber compositions.

An NBR composition, that is excellent in rubber material processability and vulcanized rubber hardness, comprising 93 to 105 parts by weight of carbon black with a carbon black grade of N330 or N550, 1.0 to 4.0 parts by weight of a vulcanization retarder, 2.0 to 5.0 parts by weight of thiazole-based and thiuram-based vulcanization accelerators, and 1.0 to 4.0 parts by weight of a sulfur-based vulcanizing agent, based on 100 parts by weight of NBR. The vulcanized molded product obtained from the NBR composition has a rubber hardness (Duro A, instant) of 85 or more according to JIS K6253 corresponding to ISO 18517, and can be effectively used as an automobile buffer material such as a stopper for electric power steering, a buffer material for nailers, a buffer material for devices equipped with hydraulic cylinders, or the like.

An NBR composition, that is excellent in rubber material processability and vulcanized rubber hardness, comprising 93 to 105 parts by weight of carbon black with a carbon black grade of N330 or N550, 1.0 to 4.0 parts by weight of a vulcanization retarder, 2.0 to 5.0 parts by weight of thiazole-based and thiuram-based vulcanization accelerators, and 1.0 to 4.0 parts by weight of a sulfur-based vulcanizing agent, based on 100 parts by weight of NBR. The vulcanized molded product obtained from the NBR composition has a rubber hardness (Duro A, instant) of 85 or more according to JIS K6253 corresponding to ISO 18517, and can be effectively used as an automobile buffer material such as a stopper for electric power steering, a buffer material for nailers, a buffer material for devices equipped with hydraulic cylinders, or the like.

The present invention is directed to a pneumatic tire comprising at least one component, the at least one component comprising a vulcanizable rubber composition, the vulcanizable rubber composition comprising at least one diene based elastomer; precipitated silica; and curatives comprising sulfur; a sulfenamide; and a compound of formula I

##STR00001##

where R.sup.1 are independently a covalent bond or a C1 to C8 linear or branched alkane diyl; R.sup.2 is C1 to C8 linear or branched alkane diyl; R.sup.3 are independently hydrogen or C1 to C8 linear or branched alkyl.

The present invention is directed to a pneumatic tire comprising at least one component, the at least one component comprising a vulcanizable rubber composition, the vulcanizable rubber composition comprising at least one diene based elastomer; precipitated silica; and curatives comprising sulfur; a sulfenamide; and a compound of formula I

##STR00001##

where R.sup.1 are independently a covalent bond or a C1 to C8 linear or branched alkane diyl; R.sup.2 is C1 to C8 linear or branched alkane diyl; R.sup.3 are independently hydrogen or C1 to C8 linear or branched alkyl.

A reinforced product, which can be used especially for reinforcing a finished rubber article, comprises one or more textile or metallic reinforcing thread(s), said thread(s) being covered with a sheath comprising a thermoplastic polymer composition, the sheathed thread(s) being themselves embedded in a rubber composition referred to as coating rubber, characterized in that this coating rubber is a composition based on at least one diene elastomer, silica as predominant reinforcing filler, and a sulfur-based vulcanization system, in which the ratio of the amounts, in phr (parts by weight per hundred parts by weight of elastomer), of sulfur and of reinforcing filler, is less than 0.08.

A reinforced product, which can be used especially for reinforcing a finished rubber article, comprises one or more textile or metallic reinforcing thread(s), said thread(s) being covered with a sheath comprising a thermoplastic polymer composition, the sheathed thread(s) being themselves embedded in a rubber composition referred to as coating rubber, characterized in that this coating rubber is a composition based on at least one diene elastomer, silica as predominant reinforcing filler, and a sulfur-based vulcanization system, in which the ratio of the amounts, in phr (parts by weight per hundred parts by weight of elastomer), of sulfur and of reinforcing filler, is less than 0.08.

The invention relates to aA reinforced product, which can be used especially for reinforcing a finished rubber article, comprisingcomprises one or more textile or metallic reinforcing thread(s), said thread(s) being covered with a sheath comprising a thermoplastic polymer composition, the sheathed thread(s) being themselves embedded in a rubber composition referred to as coating rubber, characterized in that this coating rubber is a composition based on at least one diene elastomer, a reinforcing filler, and a sulphursulfur-based vulcanization system, which system comprises a vulcanization accelerator having a vulcanization initiation time, referred to as “t0”, of less than 3.5 minutes, preferably of less than or equal to 3 minutes.