A conjugated diene rubber gel comprising 80-99 weight % of conjugated diene monomer
units and 20-1 weight % of aromatic vinyl monomer units and having a swelling index
of 16 to 70 as measured in toluene. A rubber vulcanizate made from a rubber composition
comprising this conjugated diene rubber gel and a rubber capable of being crosslinked
with sulfur exhibits good abrasion resistance and low heat-build up without deterioration
of mechanical properties, and thus, is suitable for tire materials. This conjugated
diene rubber gel can be produced with high efficiency by emulsion-polymerization
of a monomer mixture comprising 50-99.9 weight % of a conjugated diene monomer,
0-30 weight % of an aromatic vinyl monomer, 0-20 weight % of a crosslinking monomer.
