Process for producing modified polymer, modified polymer obtained by the process, and rubber composition

A process for producing a modified polymer, comprising a first and second modification process,

• the first modification process comprising modifying a polymer produced by anionic polymerization using an alkaline metal compound and/or an alkaline earth metal compound as a polymerization initiator and having an active site of an organometal in a molecule by reacting the site thereof with a hydrocarbyloxysilane compound, and
• the second modification process comprising adding a condensation accelerator to the reaction system in the middle of the above reaction, or adding a condensation accelerator to the reaction system in the middle of the above reaction and after the completion thereof,
• the condensation accelerator accelerates condensation of the modified polymer resulting in a condensed polymer,
• the condensed polymer being recovered from the system,
• wherein the polymer described above is a polymer obtained by homopolymerizing a conjugated diene compound or copolymerizing a conjugated diene compound with at least one additional monomer, and the hydrocarbyloxysilane compound described above used for the modification is at least one selected from a hydrocarbyloxysilane compound represented by Formula (I) and/or a partial condensation product thereof;
• (wherein A1 represents a monovalent group having at least one functional group selected from (thio)epoxy, (thio)isocyanate, (thio)ketone, (thio)aldehyde, imine, amide, trihydrocarbyl isocyanurate, (thio)carboxylates, metal salts of (thio)carboxylates, carboxylic anhydrides, carboxylic halides and dihydrocarbyl carbonate;
• R1 represents a single bond or a divalent inactive hydrocarbon group;
• R2 and R3 each represent independently a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms;
• n is an integer of 0 to 2, and when a plurality of OR3 is present, a plurality OR3 may be the same as or different from each other;
• and an active proton and an onium salt are not contained in the molecule), and a hydrocarbyloxysilane compound represented by Formula (II) and/or a partial condensation product thereof;
• (wherein A2 represents a monovalent group having at least on functional group selected from cyclic tertiary amine, non-cyclic tertiary amine, nitrile, pyridine, sulfide and multisulfide;
• R4 represents a single bond or a divalent inactive hydrocarbon group;
• R5 and R6 each represent independently a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms;
• m is an integer of 0 to 2, and when a plurality of OR6 is present, a plurality OR6 may be the same as or different from each other;
• and an active proton and an onium salt are not contained in the molecule).