Aromatic vinyl-conjugated diene block copolymer and production process thereof

A process for producing an aromatic vinyl-conjugated diene block copolymer by copolymerizing an aromatic vinyl monomer and a conjugated diene monomer using an active organometallic compound as an initiator in a hydrocarbon solvent, which comprises copolymerizing 5 to 60 wt. % of the aromatic vinyl monomer with 40 to 95 wt. % of the conjugated diene monomer in the following steps:

• (i) polymerizing the conjugated diene monomer;
• (ii) after step (i), polymerizing a mixture composed of the aromatic vinyl monomer and the conjugated diene monomer;
• and
• (iii) after step (ii), polymerizing the aromatic vinyl monomer;
• and further wherein a proportion of the aromatic vinyl monomer in the mixture in step (ii) to the aromatic vinyl monomer in step (iii) falls within a range of from 30:70 to 70:30.

A resin composition comprising a resin component and a rubber component, wherein the rubber component contains an aromatic vinyl-conjugated diene block copolymer which is composed of a bound aromatic vinyl unit and a bound conjugated diene unit and contains at least a block aromatic vinyl segment, said block copolymer having the following features:

• (1) a content of the bound aromatic vinyl unit in the block copolymer being 5 to 60 wt. %;
• (2) a molecular weight (A-Mp) corresponding to a peak in a molecular weight distribution curve of the block aromatic vinyl segment (A) as determined by gel permeation chromatography (GPC) being 80,000 to 300,000;
• (3) a proportion of block aromatic vinyl segment portions having a molecular weight at most a third of the molecular weight (A-Mp) corresponding to the peak in the molecular weight distribution curve of the block aromatic vinyl segment (A) as determined by GPC being 55 to 70 mol % based on the total content of the block aromatic vinyl segment (A);
• and
• (4) a molecular weight (Mp) corresponding to a peak in a molecular weight distribution curve of the block copolymer as determined by GPC being 100,000 to 600,000.

A process for preparing a resin composition by radical-polymerizing an aromatic vinyl monomer or a mixture of the aromatic vinyl monomer and another monomer copolymerizable with the aromatic vinyl monomer in the presence of a rubber component, which comprises using, as the rubber component, a rubber component containing an aromatic vinyl-conjugated diene block copolymer which is composed of a bound aromatic vinyl unit and a bound conjugated diene unit and contains at least a block aromatic vinyl segment, said block copolymer having the following features:

• (1) a content of the bound aromatic vinyl unit in the block copolymer is being 5 to 60 wt. %;
• (2) a molecular weight (A-Mp) corresponding to a peak in a molecular weight distribution curve of the block aromatic vinyl segment (A) as determined by gel permeation chromatography (GPC) being 80,000 to 300,000;
• (3) a proportion of block aromatic vinyl segment portions having a molecular weight at most a third of the molecular weight (A-Mp) corresponding to the peak in the molecular weight distribution curve of the block aromatic vinyl segment (A) as determined by GPC being 55 to 70 mol % based on the total content of the block aromatic vinyl segment (A);
• and
• (4) a molecular weight (Mp) corresponding to a peak in a molecular weight distribution curve of the block copolymer as determined by GPC being 100,000 to 600,000.