Process for producing hydrogenated block copolymer, hydrogenated block copolymer obtained by the process, and composition thereof

A hydrogenated block copolymer, comprising a copolymer represented by formula P′, (P′)n—Z, or both, wherein P′ is a copolymer chain having one or more aromatic vinyl compound polymer blocks (A) and one or more hydrogenated conjugated diene polymer blocks (B);

• n is an integer of 1 to 6;
• and Z represents part of a silane coupling agent of formula (II) or part of a silane coupling agent of formula (III):
• SiY4 (II)
• R1mY3-mSi-A-SiY3-mR1m (III)
• wherein each R1 is independently a hydrogen atom, an aryl group having 6 to 12 carbon atoms, or a linear or branched alkyl group having 1 to 12 carbon atoms;
• each Y is independently a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an alkoxy group, a carboxyl group, or a carboxylic acid ester group;
• A is a single bond or a linear alkylene group having 1 to 20 carbon atoms;
• and
• m is 0 or 1,
• wherein the hydrogenated block copolymer has a branching index of 2.3 or more and a number of functional groups derived from a coupling agent in the hydrogenated block copolymer is 1.5 or less per block copolymer molecule,
• wherein the hydrogenated block copolymer is obtained by a method comprising:
• (a-1) polymerizing monomers with an alkyl lithium compound as an initiator in an inert solvent, thereby obtaining a living anionic polymer of formula (I):
• P—X (I)
• where P is a copolymer chain comprising, in reacted form, an aromatic vinyl compound polymer block (A) and a conjugated diene polymer block (B), and X is an active terminal of the living anionic polymer;
• (a-2) reacting a silane coupling agent having a functionality of at least four, with the living anionic polymer of formula (I) after the polymerizing (a-1) monomers to obtain a block copolymer;
• (b) hydrogenating the block copolymer to obtain a hydrogenated block copolymer;
• (c) isolating the hydrogenated block copolymer to obtain an isolated hydrogenated block copolymer;
• and
• (d) adding a Lewis base to the block copolymer or the hydrogenated block copolymer after said (a-2) reacting of the silane coupling agent with the living polymer such that (i) a functional group of the silane coupling agent, (ii) an unreacted functional group present in a coupling agent residue in the block copolymer or the hydrogenated block copolymer, or both (i) and (ii) is deactivated with the Lewis base, said deactivating being carried out prior to said (c) isolating,
• wherein
• the Lewis base is at least one member selected from the group consisting of an alkyl lithium compound, an alkyl sodium compound, an alkyl potassium compound, an alkyl magnesium halide compound, a dialkyl copper lithium compound, and lithium amide compound.