Process for producing modified polymer rubber

A process for producing a modified polymer rubber, which comprises the steps of:

• (1) reacting one part by mol of an organoalkali metal compound with n±0.7 (n is an integer of 3 or more) parts by mol of a compound represented by the following formula (1) to produce a reaction mixture,
• 3
• wherein R1 is an amino group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof,
• (2) polymerizing in the presence of the produced reaction mixture an aromatic vinyl monomer and a conjugated diene monomer in a hydrocarbon solvent, and after completion of the polymerizing, stirring for at least 30 minutes, to produce a polymerization reaction mixture,
• (3) repeating such an operation n−2 times that (i) an aromatic vinyl monomer and a conjugated diene monomer are added to the produced polymerization reaction mixture, and polymerized, and (ii) after completion of the polymerizing, stirring is carried out for at least 30 minutes, and thereby producing a modified polymer rubber, whose both ends and n−2 positions in its chain are modified by the compound represented by the formula (1), and
• (4) modifying further the produced modified polymer rubber with a modifier having a functional group, and thereby producing a modified polymer rubber, whose initial end is modified by the compound represented by the formula (1), whose terminal end is modified by two functional groups, wherein one of said two functional groups is derived from the compound represented by the formula (1), and another thereof is derived from the modifier, and each of n−2 positions in whose chain is modified by one functional group of the compound represented by the formula (1)