Process for preparing a bituminous binder composition
View Patent ↗A block copolymer composition including a diblock copolymer (I) having one block of a monovinylaromatic hydrocarbon and one block of a conjugated diene having a peak molecular weight from 30,000 to 78,000 and one or more block copolymers (ii) comprising at least two blocks of monovinylaromatic hydrocarbon and at least one block of conjugated diene, the block copolymer selected from linear triblock copolymers having a peak molecular weight that is 1.5 to 9.0 times the peak molecular weight of the diblock copolymer, and mixtures thereof, wherein the ratio of (i) to (ii) is greater than 1:1.
1. A block copolymer composition comprising
(i) a diblock copolymer comprising one block of a monovinylaromatic hydrocarbon and one block of a conjugated diene having a peak molecular weight from 30,000 to 78,000 and a vinyl content from 35 to 80 mol percent based on the number of repeat monomer units in the conjugated diene block, and
(ii) a block copolymer comprising at least two blocks of monovinylaromatic hydrocarbon and at least one block of conjugated diene, the block copolymer selected from the group consisting of linear triblock copolymers having a peak molecular weight that is 1.5 to 3.0 times the peak molecular weight of the diblock copolymer, multiarm coupled block copolymers having a peak molecular weight that is 1.5 to 9.0 times the peak molecular weight of the diblock copolymer, and mixtures thereof, wherein each block copolymer has a vinyl content from 35 to 80 mol percent based on the number of repeat monomer units in the conjugated diene block, wherein the melt index for the block copolymer composition is from about 20 g/10 min to about 35 g/10 min as determined by ASTM D-1238, condition G (200° C., 5 kg) and wherein the ratio of (i) to (ii) in the block copolymer composition is greater than 1:1.
2. The block copolymer composition of claim 1 wherein the ratio of (i) to (ii) is greater than or equal to 3:2, the diblock copolymer (i) is of the formula A-B and the optional block copolymer (ii) is selected from the group consisting of block copolymers of the formula A-B-A and (A-B)nX wherein with regard to the formulas A is a block of monovinyl aromatic hydrocarbon, B is a block of conjugated diene, n is an integer from 2 to 6 and X is a coupling agent residue.
3. The block copolymer composition of claim 2 wherein the block copolymer composition comprises A-B and A-B-A wherein each A is styrene and each B is butadiene, the peak molecular weight of A-B is from 48,000 to 78,000 and the vinyl content is from 46 to 70 mol percent based on the number of repeat monomer units in the conjugated diene block of A-B, and the peak molecular weight of A-B-A is 1.8 to 2.5 times the peak molecular weight of A-B and the vinyl content is from 46 to 70 mol percent based on the number of repeat monomer units in the conjugated diene block of A-B-A, and the polystyrene content of A-B is from 25 to 35% and the polystyrene content of A-B-A is from 25 to 35%.