The present invention provides, inter alia, a method for producing a masterbatch in which the dispersibility of microfibrillated plant fibers is further increased to obtain excellent processability and improved rubber properties such as fuel economy, tensile strength, and elongation at break. The present invention relates to a method for producing a masterbatch, the method including step (I) of mixing a rubber latex with microfibrillated plant fibers oxidized with an N-oxyl compound to obtain a mixture, and coagulating the mixture by adjusting its pH to 2 to 6.

The invention relates to a process for producing a vulcanizable composite material, comprising the steps of: a) producing or providing a textile strength member, b) treating the textile strength member with an aqueous dispersion for adhesive activation of the textile strength member and to obtain an adhesion-activated textile strength member and c) introducing the adhesion-activated textile strength member into a crosslinkable rubberization mixture to obtain the vulcanizable composite material, wherein the aqueous dispersion is essentially free of free resorcinol and resorcinol precondensates, especially resorcinol-formaldehyde precondensates, and is free of free formaldehyde and formaldehyde-releasing substances, wherein the crosslinkable rubberization mixture is processible by vulcanization to give a crosslinked rubberization mixture which is at least partly transmissive to visible light at least in sections.

The present invention provides: a rubber composition obtained by mixing 30 to 80 parts by mass of carbon black, whose DBP absorption value and CTAB adsorption specific surface area satisfy the following relational formulas (I) and (II), into 100 parts by mass of a rubber component, wherein macrodispersion D(%) of the carbon black in the rubber composition is 1% or more and less than 10%, and the rubber composition has high performance and excellent processability such as roll workability and the like; and a rubber product such as a tire having reduced rolling resistance and excellent fatigue resistance and abrasion resistance.
DBP absorption value(cm.sup.3/100 g)<3.0(CTAB adsorption specific surface area(m.sup.2/g))270(I)
DBP absorption value(cm.sup.3/100 g)<115(II)
CTAB adsorption specific surface area(m.sup.2/g)<230(III).

The invention relates to a rubber composition based on at least one diene elastomer, a reinforcing filler comprising at least carbon black having a CTAB specific surface of greater than or equal to 130 m.sup.2/g, a plasticizing oil and also a crosslinking system, the dispersion of the filler in the elastomeric matrix having a Z score of greater than or equal to 70.

Methods to make a silica elastomer composite with a destabilized dispersion of a never-dried, or as-produced, precipitated silica are described, along with silica elastomer composites made from the methods. The advantages achieved with the methods are further described.

Provided is a process for producing a wet masterbatch which, without deteriorating a reinforcing property of a rubber composition and rubber physical properties, micronizes a filler slurry by controlling an amount of functional groups on a filler surface, and improves filler dispersibility in the rubber wet masterbatch and the rubber composition. The process for producing a wet masterbatch comprises: a step of producing a slurry solution having a pH of 8 or more by dispersing carbon black having an average amount of surface acidic functional groups (eq/m.sup.2) of 0.15 or more and less than 3.00; a step of producing a mixture by mixing the slurry solution and a rubber latex solution in a liquid phase; and a step of drying the mixture.

The present invention provides an effective method for fractionating rubber particles in natural rubber latex by particle size, and effective methods for transporting or preserving rubber particles. The present invention relates to a method for fractionating rubber particles in natural rubber latex by particle size, the method including centrifuging natural rubber latex in at least four stages at forces of 800 to 3,000g, 6,500 to 10,000g, 17,000 to 22,000g, and 40,000 to 60,000g to fractionate rubber particles. The present invention also relates to methods for transporting or preserving rubber particles, the methods including the steps of adding a buffer solution and an antioxidant to natural rubber latex or rubber particles fractionated from natural rubber latex; and freezing a mixture prepared in the above step.

The invention relates to a rubber composition based on at least one diene elastomer, a reinforcing filler comprising at least carbon black having a CTAB specific surface of greater than or equal to 130 m.sup.2/g, a plasticizing oil and also a crosslinking system, the dispersion of the filler in the elastomeric matrix having a Z score of greater than or equal to 70.

A masterbatch composition of elastomer and from 20 to 100 parts per hundred parts elastomer of fibrous micropulp wherein the micropulp has fibers with a volume weighted average fiber length of from 20 to 200 micrometers as measured by laser diffraction, a relative specific surface area of from 30 to 600 square meter per gram as measured by nuclear magnetic resonance and the fibers selected from the group consisting of aromatic polyamide, aromatic copolyamide, polyacrylonitrile and polyazole.

The present invention provides a method for producing a rubber composition for tire tread, which is prepared by mixing 100 parts by mass of a rubber component containing 60 to 80 parts by mass of a natural rubber and 20 to 40 parts by mass of a modified conjugated dienic polymer having one or more functional groups having another atom than carbon and hydrogen, and 40 to 60 parts by mass of carbon black having a nitrogen adsorption specific surface area (N.sub.2SA) of 40 to 95 m.sup.2/g and a hydrogen release rate of 0.37% by mass or more based on 100 parts by mass of the rubber component, wherein the temperature of the rubber composition at the time of discharge in the kneading step for mixing carbon black therein is 170 C. or higher, a rubber composition obtained according to the production method, and a tire using the rubber composition. According to the production method for a rubber composition, the heat generation property of the rubber composition can be reduced, and the dynamic storage elastic modulus thereof can be increased. By using the rubber composition obtained according to the production method as tread, there can be provided a tire having not only reduced rolling resistance but also improved abrasion resistance, anti-tear performance (tear resistance) and cut resistance.