Block copolymers and polymer modified bitumen therefrom
Disclosed herein are linear block copolymers of formula A-B-A′ or A-B*B-A′, wherein blocks A and A′ are polystyrene blocks, block B is a poly(conjugated diene) block and * is a coupling agent having a vinyl content of from 10-60 mol %. The block copolymers have a polystyrene content of from 20-35 wt. %, relative to the overall weight of the block copolymer, and a molecular weight of from 200,000-300,000 g/mol. The block copolymers can be used with a wide variety of asphalt grades, and are valuable for producing homogeneous polymer modified asphalt compositions having an effective combination of performance properties, such as acceptable viscosity, good elastic response to an applied stress, and a low non-recoverable creep compliance. The combination of vinyl content and polymerization technology allows a high solution concentration during polymerization without excessive processing viscosity.
1. A polymer modified bitumen composition comprising:
a block copolymer in an amount of 1 to 25 wt. % relative to the overall weight of the composition;
at least a bitumen;
optionally at least one crosslinking agent; and
optionally additional additives;
wherein the block copolymer has a formula of A-B-A′ or (A-B)n-X—(B-A′)m,
wherein:
A and A′ are vinyl aromatic blocks having different molecular weights, A and A′ have different molecular weights, with the molecular weight difference ranging from 3,000 to 8,000 g/mol,
B is a conjugated diene block,
B has an average vinyl content ranging from 20-60 mol %,
n and m>=1, and X is a coupling agent;
wherein
the block copolymer has a polystyrene content of 20-35 wt. %, relative to the overall weight of the block copolymer, and
the block copolymer has a molecular weight of 200,000-300,000 g/mol
wherein a polymer modified bitumen composition containing 3 wt. % of the block copolymer has a Multiple Stress Creep Recovery, % R, of >=59% at 3.2 kPa, 64° C., and a Multiple Stress Creep Recovery Jnr of <0.3 kPa −1 at 3.2 kPa, 64° C.
2. The polymer modified bitumen composition of claim 1 , wherein the composition is used in an asphalt pavement product or an asphalt roofing product.
3. The polymer modified bitumen composition of claim 1 , wherein the composition is used in new pavements, pavement preservation, pavement rehabilitation, hot mix asphalt, cold mix asphalt, warm mix asphalt, and emulsified bitumen based asphalt.
4. The polymer modified bitumen composition of claim 1 , wherein the composition is used in a modified bitumen membrane, self-adhesive membrane, impact resistant shingle, laminate, shingle tab adhesive, shingle body, sheet, roll, pipe coating, sealant, sound damping membrane, carpet, railroad construct, crack filler, chip seal, and micro surfacing.
5. The polymer modified bitumen composition of claim 1 , wherein the block copolymer has the formula (A-B) n —X—(B-A′) m with n and m having a value of 1.
6. The polymer modified bitumen composition of claim 5 , wherein the block copolymer further comprises up to 25 wt. % based on the total weight of the block copolymer, a second block copolymer having the structure (A-B) n —X—(B-A′) m , with n and m having a value of >1 and <=5.
7. The polymer modified bitumen composition of claim 1 , wherein the block copolymer has a molecular weight of 220,000-270,000 g/mol.
8. The polymer modified bitumen composition of claim 1 , wherein block B has a vinyl content of 25-55 mol %.
9. The polymer modified bitumen composition of claim 1 , wherein the vinyl is distributed evenly over the conjugated diene block B.
10. The polymer modified bitumen composition of claim 1 , wherein the vinyl is distributed with a gradient over the conjugated diene block B.
11. The polymer modified bitumen composition of claim 1 , wherein the vinyl is distributed in one or more distinct blocks with low and high vinyl in the conjugated diene block B.
12. The polymer modified bitumen composition of claim 1 , wherein the block copolymer is produced by any of sequential anionic polymerization, or sequential anionic polymerization followed by coupling.
13. The polymer modified bitumen composition of claim 12 , wherein the block copolymer has a formula A-B-A′, and wherein the block copolymer is produced by sequential anionic polymerization.
14. The polymer modified bitumen composition of claim 12 , wherein the block copolymer has a formula (A-B) n —X—(B-A′) m , and wherein the block copolymer is produced by sequential anionic polymerization followed by coupling with a coupling agent.
15. The polymer modified bitumen composition of claim 14 , wherein the coupling agent is selected from the group of methoxysilanes, halogenated silanes, epoxies, adipates, benzoates, carbon dioxide, dimethyldimethoxysilane, dimethyldibchlorosilane, di-ethyl-adipate, and mixtures thereof.
16. The polymer modified bitumen composition of claim 12 , wherein at least a microstructure modifier is added to the polymerization process to control the vinyl content of block B.
17. The polymer modified bitumen composition of claim 16 , wherein the microstructure modifier is selected from ethers, amines, dialkylethers of glycols, and mixtures thereof.