Patent ID: 7858693

Claim:
A block copolymer composition comprising: (a) 100 parts by weight of a solid block copolymer wherein: (i) said block copolymer comprises at least two A blocks and at least one B block, each A block independently selected from mono alkenyl arene polymer blocks and each B block independently selected from (1) polymer blocks having at least one conjugated diene and at least one mono alkenyl arene and having a random distribution; and (2) polymer blocks having at least one conjugated diene and at least one mono alkenyl arene and having a controlled distribution; (ii) each A block having a peak molecular weight between about 3,000 and about 60,000 and each B block having a peak molecular weight (MW 1 ) between about 20,000 and about 200,000; (iii) the total amount of mono alkenyl arene in the block copolymer is about 30 percent weight to about 85 percent weight; and (iv) the weight percent of mono alkenyl arene in each B block (S 1 ) is between about 5 percent and about 75 percent; and (b) 5 to 250 parts by weight of a tailored softening modifier which comprises a conjugated diene and is structurally related to the character of the B block of said block copolymer wherein: (i) the ratio (MW 2 )/(MW 1 ) of the peak molecular weight of said softening modifier (MW 2 ) to the peak molecular weight of said B block of said block copolymer (MW 1 ) is 0.01 to 1.0, with a minimum molecular weight (MW 2 ) of 2,000; (ii) the weight percent of mono alkenyl arene in each softening modifier (S 2 ) is between about 5 percent and about 75 percent and the ratio of S 2 /S 1 is between 0.5 and 1.5; and (c) wherein said softening modifier is polymerized in solution in the presence of a solvent in a second reactor to form a second solution and combined with a first solution prepared in a first reactor having a solvent to form a common solution, wherein said block copolymer is polymerized in said first solution or common solution, and (d) the solvent is removed from the common solution after polymerization of said block copolymer, providing an intimate mixture of said block copolymer and said tailored softening modifier.