Process for producing thermoplastic elastomer, and thermoplastic elastomer

A method for producing a thermoplastic elastomer, the method comprising:

• forming a first block by copolymerizing a C4-C7 isoolefin monomer and alkylstyrene in the presence of a polymerization initiator;
• and
• forming a second block by polymerizing aromatic vinyl monomers, wherein
• the thermoplastic elastomer comprises the first block and the second block,
• the formation of the first block comprises adding the alkylstyrene to a reaction solution containing the polymerization initiator and the C4-C7 isoolefin monomer by drip-feeding for not less than 10% of a total time of the formation of the first block,
• the alkylstyrene is represented by the following general formula (1):
• wherein R1 and R2 are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, and a C1-C5 halogenated alkyl group,
• the alkylstyrene is added such that an amount of unreacted alkylstyrene is maintained at a molar ratio of not more than 1/90 relative to a total amount of the isoolefin monomer during the formation of the first block, and
• the polymerization initiator is represented by the following general formula (2):
• wherein R3 is each independently a hydrogen atom or a C1-C6 monovalent hydrocarbon group;
• R4 is a monovalent or polyvalent aromatic hydrocarbon group, or a monovalent or polyvalent aliphatic hydrocarbon group;
• X is each independently a halogen atom, a C1-C6 alkoxyl group, or a C1-C6 acyloxy group;
• and n is an integer of 1 to 6.