Blown asphalt compositions
View Patent ↗A process for preparing compatible, selectively hydrogenated block copolymer-modified bituminous compositions comprising blowing a mixture of the block copolymer and bitumen with an oxidizing gas at temperatures of at least 375° C. for at least 75 minutes. The modifying polymer is a selectively hydrogenated styrenic block copolymer and no blowing catalyst is required. Stable bituminous compositions comprising 6 to 25 parts by weight of block copolymer per 100 parts of asphalt are also provided as well as their application as roofing shingles.
1. A process for preparing a bituminous composition comprising
i) heating 100 parts by weight bitumen to at least 375° F.,
ii) adding from 6 to 25 parts by weight of a selectively hydrogenated block copolymer having at least one A block of a polymerized monoalkenyl arene and at least one B block of a polymerized and hydrogenated conjugated diene,
iii) stirring the mixture, and
iv) blowing an oxygen-containing gas through the mixture at a gas flow rate of at least 5 lpm per kg of the bituminous composition for a time of at least 75 minutes in the absence of a blowing catalyst.
2. The process of claim 1 wherein the selectively hydrogenated block copolymer has the general formula
S-EB-S or (S-EB)nX
where S is a styrene block, EB is a hydrogenated butadiene block, X is the residue of a coupling agent and n is from 2 to 8.
3. The process of claim 2 wherein the styrene block has a weight average molecular weight from 5,000 to 30,000, and the total molecular weight of the block copolymer is from 50,000 to 300,000.
4. The process of claim 3 wherein the styrene content of the block copolymer is from 20 to 40 wt %.
5. The process of claim 2 wherein the EB block has a vinyl content from 20 to 80 mol % prior to hydrogenation.
6. The process of claim 1 wherein the oxygen-containing gas is air.
7. The process of claim 1 wherein the resulting bituminous composition has a softening point of at least 190° F.
8. The process of claim 1 wherein the resulting bituminous composition has a PEN value from 20 to 30 units at 25° C.
9. The process of claim 1 wherein the resulting bituminous composition has a Brookfield viscosity from 200 to 1400 cps at 400° F.
10. The process of claim 1 wherein 7 to 15 parts by weight of a selectively hydrogenated block copolymer is added in step ii) for each 100 parts by weight of bitumen.
11. A stable, polymer-modified bituminous composition made by the process comprising
i) heating 100 parts by weight bitumen to at least 375° F.,
ii) adding from 6 to 25 parts by weight of a selectively hydrogenated block copolymer having at least one A block of a polymerized monoalkenyl arene and at least one B block of a polymerized and hydrogenated conjugated diene,
iii) stirring the mixture, and
iv) blowing an oxygen-containing gas through the mixture at a gas flow rate of at least 5 lpm per kg of the bituminous composition for a time of at least 75 minutes in the absence of a blowing catalyst having a softening point of at least 190° F.
12. The bituminous composition of claim 11 wherein the selectively hydrogenated block copolymer has the general formula
S-EB-S or (S-EB)nX
where S is a styrene block, EB is a hydrogenated butadiene block, X is the residue of a coupling agent and n is from 2 to 8.
13. The bituminous composition of claim 12 wherein the styrene block has a weight average molecular weight from 5,000 to 30,000, and the total molecular weight of the block copolymer is from 50,000 to 300,000.
14. The bituminous composition of claim 13 wherein the styrene content of the block copolymer is from 20 to 40 wt %.
15. The bituminous composition of claim 11 wherein the EB block has a vinyl content from 20 to 80 mol % prior to hydrogenation.
16. The bituminous composition of claim 11 having PEN value from 20 to 30 units at 25° C.
17. The bituminous composition of claim 11 having a viscosity from 200 to 1400 cps at 400° F.
18. The bituminous composition of claim 11 having a ring and bail softening point of at least 200° F.
19. A roofing shingle comprising the bituminous composition of claim 11 and a non-woven glass mat.
20. The roofing shingle of claim 19 wherein the bituminous composition comprises from 30 to 50 wt % of the total shingle weight.
21. The roofing shingle of claim 19 wherein the selectively hydrogenated block copolymer has the general formula
S-EB-S or (S-EB)nX
where S is a styrene block, EB is a hydrogenated butadiene block, X is the residue of a coupling agent and n is from 2 to 8.
22. The roofing shingle of claim 21 wherein the styrene block has a weight average molecular weight from 5,000 to 30,000, the total molecular weight of the block copolymer is from 50,000 to 300,000, and the EB block has a vinyl content from 20 to 80 mol % prior to hydrogenation.