Block copolymers comprising a mixed block derived from isoprene and butadiene and compositions comprising them
Adhesive compositions, comprising a. one or more block copolymers comprising at least two poly(vinyl aromatic) blocks and at least one predominantly poly(conjugated diene) block, b. one or more tackifying resins, and c. optionally one or more plasticizers, characterized in that the block copolymer component (i) comprises at least one block of a randomly copolymerised mixture of isoprene and butadiene in a weight ratio (I:B) in the range of from 99:1 to 80:20, and block copolymers to be used therein.
1 . An adhesive composition, comprising
a. one or more block copolymers comprising at least two predominantly poly(vinyl aromatic) blocks and at least one predominantly poly(conjugated diene) block,
b. one or more tackifying resins, and
c. optionally one or more plasticizers,
characterized in that the block copolymer component (i) comprises at least one block of a randomly copolymerised mixture of isoprene and butadiene in a weight ratio (I:B) in the range of from 99:1 to 80:20.
2 . The adhesive composition of claim 1 , wherein the randomly polymerised mixture of isoprene and butadiene has a weight ratio in the range of from 95:5 to 80:20.
3 . The adhesive composition of claim 2 , wherein the randomly polymerised mixture of isoprene and butadiene has a weight ratio in the range of from 95:10 to 82:18.
4 . The adhesive composition of claim 1 , wherein the block copolymer component (i) comprises blocks A, having a true molecular weight in the range of from 9,500 to 25,000.
5 . The adhesive composition of claim 1 , wherein the block copolymer component (i) has a poly(vinyl aromatic) content of from 15 to 45 wt %.
6 . The adhesive composition of claim 1 , wherein the block copolymers are of the formula
A-C-A (1) or (A-C) n —X (2),
wherein each A independently is a polymer block of an aromatic vinyl compound, and C is a mixed polymer block (I/B) of isoprene (I) and butadiene (B).
7 . The adhesive composition of claim 1 , wherein each block copolymer contains 1,2-vinyl bonds and/or 3,4-vinyl bonds in a proportion of at most 15 wt %.
8 . The adhesive composition of claim 7 , wherein component (i) further comprises an intermediate diblock in a weight ratio of coupled polymer of formula (1) or (2) to diblock of 100/0 to 40/60.
9 . The adhesive composition of claim 7 , wherein the midblock has a Tg of −62° C. or lower.
10 . Tapes, labels and sanitary articles obtainable by application of the adhesive composition of claim 1 .
11 . A block copolymer, characterized in that it comprises at least two poly(vinyl aromatic) blocks and at least one block of a randomly copolymerized mixture of isoprene and butadiene in a weight ratio (I:B) in the range of from 99:1 to 80:20.
12 . The block copolymer of claim 11 , wherein the randomly copolymerized mixture of isoprene and butadiene has a weight ratio of from 95:5 to 80:20.
13 . The block copolymer of claim 11 , wherein the blocks A have a true molecular weight in the range of from 9,500 to 25,000.
14 . The block copolymer of claim 12 , wherein the blocks A have a true molecular weight in the range of from 9,500 to 25,000.
15 . The block copolymer of claim 11 , having a poly(vinyl aromatic) content in the range of from 15 to 45 wt %.
16 . The block copolymer of claims 12 , having a poly(vinyl aromatic) content in the range of from 15 to 45 wt %.
17 . The block copolymer of claim 13 , having a poly(vinyl aromatic) content in the range of from 15 to 45 wt %.
18 . The block copolymer of claim 11 wherein the block copolymers are of the formula
A-C-A (1) or (A-C) n —X (2),
wherein each A independently is a polymer block of an aromatic vinyl compound, and C is a mixed polymer block (I/B) of isoprene (I) and butadiene (B).
19 . The block copolymer of claim 11 , wherein each block copolymer contains 1,2-vinyl bonds and/or 3,4-vinyl bonds in a proportion of at most 15 wt %.
20 . The block copolymer of claim 18 , wherein the midblock has a Tg of −2° C. or less.