Abstract: It could be helpful to provide a rubber composition that can achieve both reinforcement property and low loss property at a high level. In order to solve the aforementioned problems, the disclosure is a rubber composition comprising a rubber component, carbon black, and silica, wherein the silica has a CTAB adsorption specific surface area of 250 m2/g or more; the silica has a diameter in the form of aggregates (DCPS) and a primary particle diameter (DI), as measured by disk centrifugal particle size analysis, that satisfy: 700?DCPS3/DI3?300 (1); the rubber component contains at least one selected from natural rubber and polyisoprene rubber, and at least one selected from modified butadiene rubber and modified styrene butadiene rubber; and the carbon black is contained by a mass ratio of 70% or more with respect to the total mass content of the carbon black and the silica.

Abstract: The natural rubber of the present invention is obtained by gelatinizing or multi-coupling a natural rubber latex or a natural rubber and comprises 15% by mass or more of a high molecular weight component, P1, having a molecular weight of 5,000,000 to 50,000,000 and 40% by mass or less of an ultrahigh molecular weight component, P2, having a molecular weight of exceeding 50,000,000, and the relation between mass % of P1 and mass % of P2 is 1.5×mass % of P1?mass % of P2, each measured by the following measuring method, wherein a measuring method for a rubber molecular weight is measured by means of a field flow fractionation equipment with a multi-angle light scattering detector for a soluble part of a centrifuged rubber solution at a centrifugal acceleration of 10,000 to 1,000,000 G.

Abstract: A multiple-unit sustained release tablet characterized by consisiting of a granular part and a powdery part, each granule comprising a matrix composed of a water-insoluble polymer and an active ingredient. Another tablet characterized in that each granule is coated with a release-controlling film. The object of the present invention is to provide a multiple-unit sustained release tablet showing little change in dissolution speed caused by the compression in the tableting step.