Block copolymer and polymer modified bituminous binder composition for use in base course asphalt paving application
The present invention provides a polymeric composition that includes a coupled block copolymer having a plurality of arms comprising at least two blocks of a monovinylaromatic hydrocarbon that are located on at least two of the plurality of arms, and at least one block of a conjugated diene located on at least one of the plurality of arms, and optionally one or more block copolymers comprising at least one block of monovinylaromatic hydrocarbon and at least one block of a conjugated diene, the block copolymer may be selected from linear copolymers, linear triblock copolymers, multiarm coupled block copolymers, and mixtures thereof. The molecular weight of the polymeric composition is in the range from about 100 kg/mol to about 400 kg/mol.
1. An asphalt paving laminate, comprising a base course and a wearing course bound atop said base course, said base course comprising:
about 90 to about 98% by weight of a bitumen component having a PEN value of from about 20 dmm to about 55 dmm according to ASTM Method D5 at 25° C.; and
about 2 to about 10% by weight of a diblock copolymer composition comprising
(i) a copolymer comprising one polymer block of styrene and one polymer block of butadiene having a peak molecular weight from about 30,000 to about 78,000 and a vinyl content from about 35 to about 80 mol percent based upon the repeat monomer units of the butadiene block, and
(ii) one or more block copolymers comprising two polymer blocks of styrene and one polymer block of butadiene, the block copolymer selected from linear triblock copolymers having a peak molecular weight that is 1.5 to 3 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 butadiene block, wherein the ratio of (i) to (ii) in the copolymer composition is present at a ratio of greater than 1:1, wherein the base course is in a paving application and has a PEN value in the range of 10 dmm to 100 dmm according to ASTM Method D5 at 25° C.
2. The asphalt paving laminate of claim 1 , wherein the copolymer (i) is of the formula A-B and the block copolymer (ii) is selected from 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 asphalt paving laminate of claim 1 , 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 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 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%, wherein said PEN value of said base course is in the range of 20 to 75 dmm.
4. The asphalt paving laminate of claim 1 , further comprising the addition of a block copolymer of the formula C-D-C or (C-D)nX, wherein C is styrene, D is butadiene, isoprene or mixtures thereof, n is an integer from 2 to 6 and X is a coupling agent residue, and the additional block copolymer is added in an amount up to 30% by weight, of the total amount of block copolymer added.