Styrene butadiene block copolymers for film applications
We disclose a monovinylarene-conjugated diene block copolymer containing a plurality of monovinylarene-conjugated diene mixed blocks, wherein each mixed block contains conjugated diene units and monovinylarene units in a weight ratio of about 0.05 to about 0.33. We also disclose a composition containing (a) from about 50 parts by weight to about 95 parts by weight of the monovinylarene-conjugated diene block copolymer and (b) from about 5 parts by weight to about 50 parts by weight of polystyrene; wherein the monovinylarene-conjugated diene block copolymer and the polystyrene total 100 parts by weight. We further disclose a method of shrink-wrapping an object or a group of objects by wrapping the object or the group of objects with a film containing the composition, to yield a wrapped object or group of objects, and heating the wrapped object or group of objects to a temperature and for a duration sufficient to shrink the film in at least a first direction, to yield a shrink-wrapped object or group of objects.
1. A monovinylarene-conjugated diene block copolymer formed through a charge order i-C-C-C-i-C-C-B-CA, wherein i is a polymerization initiator charge, B is a conjugated diene charge that comprises between about 5 phm and about 50 phm conjugated diene units, C is a monovinylarene-conjugated diene charge comprising a weight ratio of conjugated diene units to monovinylarene units that is between about 0.05 and about 0.33, and CA is a coupling agent charge.
2. The monovinylarene-conjugated diene block copolymer of claim 1 , wherein B comprises from about 10 phm to about 20 phm conjugated diene units.
3. The monovinylarene-conjugated diene block copolymer of claim 1 , wherein the weight ratio of conjugated diene units to monovinylarene units of C is between about 0.08 and about 0.26.
4. The monovinylarene-conjugated diene block copolymer of claim 1 , wherein the weight ratio of conjugated diene units to monovinylarene units of C is about 0.2.
5. The monovinylarene-conjugated diene block copolymer of claim 1 , wherein B comprises from about 10 phm to about 35 phm conjugated diene units.
6. The monovinylarene-conjugated diene block copolymer of claim 5 , wherein the weight ratio of conjugated diene units to monovinvlarene units of C is between about 0.08 and about 0.26.
7. The monovinylarene-conjugated diene block copolymer of claim 1 , in the form of a film having a thickness of about 0.5 mil to about 3 mil and having been oriented at about 70° C., wherein the film has a shrinkage in at least one direction of about 75% at about 100° C.
8. The monovinylarene-conjugated diene block copolymer of claim 7 , wherein the film has a natural shrinkage of less than about 10% after 7 days.
9. The monovinylarene-conjugated diene block copolymer of claim 7 , wherein the film has a haze of less than about 10%.
10. The monovinylarene-conjugated diene block copolymer of claim 7 , wherein the film has a haze of less than about 5%.
11. The monovinylarene-conjugated diene block copolymer of claim 7 , wherein the film has a haze of less than about 3%.
12. A monovinylarene-conjugated diene block copolymer, comprising:
a distal monovinylarene block resulting from a monovinylarene charge comprising from about 10 phm to about 40 phm monovinylarene units;
a proximal conjugated diene block resulting from a conjugated diene charge comprising from about 10 phm to about 35 phm conjugated diene units; and
four consecutive monovinylarene-conjugated diene mixed blocks disposed directly between the distal monovinylarene block and the proximal conjugated diene block, wherein each monovinylarene-conjugated diene mixed block contains conjugated diene units and monovinylarene units with a weight ratio of conjugated diene units to monovinylarene units of about 0.2.
13. The monovinylarene-conjugated diene block copolymer of claim 12 , wherein the monovinylarene charge comprises from about 15 phm to about 35 phm monovinylarene units.
14. The monovinylarene-conjugated diene block copolymer of claim 13 , wherein the monovinylarene charge comprises about 30 phm monovinylarene units.
15. The monovinylarene-conjugated diene block copolymer of claim 12 , wherein the conjugated diene charge comprises from about 11 phm to about 25 phm conjugated diene units.
16. The monovinylarene-conjugated diene block copolymer of claim 15 , wherein the conjugated diene charge comprises from about 15 phm to about 16 phm conjugated diene units.
17. A shrink film, comprising:
about 20% polystyrene; and
a monovinylarene-conjugated diene block copolymer, comprising:
a proximal conjugated diene block resulting from a conjugated diene charge comprising from about 10 phm to about 35 phm conjugated diene units; and
at least four monovinylarene-conjugated diene mixed blocks, wherein each monovinylarene-conjugated diene mixed block contains conjugated diene units and monovinylarene units with a weight ratio of conjugated diene units to monovinylarene units of about 0.05 to about 0.33;
wherein the shrink film has a shrinkage in at least one direction of at least about 60% at about 100° C. and a haze of less than about 10%.
18. The shrink film of claim 17 , wherein the shrink film comprises a haze of less than about 8%.
19. The shrink film of claim 18 , wherein the shrink film comprises a haze of less than about 3%.
20. The shrink film of claim 17 , wherein the shrink film has a shrinkage in at least one direction of at least about 70% at about 100° C.
21. The shrink film of claim 17 , comprising 2% or less high impact polystyrene (HIPS).
22. The shrink film of claim 17 , wherein the shrink film comprises a natural shrinkage less than about 6% after 3 days.
23. A monovinylarene-conjugated diene block copolymer formed through a charge order i-A-C-C-i-C-C-B-CA, wherein i is a polymerization initiator charge, A is a monovinylarene charge, B is a conjugated diene charge that comprises between about 5 phm and about 50 phm conjugated diene units, C is a monovinylarene-conjugated diene charge comprising a weight ratio of conjugated diene units to monovinylarene units that is between about 0.05 and about 0.33, and CA is a coupling agent charge.
24. The monovinylarene-conjugated diene block copolymer of claim 23 , wherein B comprises from about 10 phm to about 20 phm conjugated diene units.
25. The monovinylarene-conjugated diene block copolymer of claim 23 , wherein the weight ratio of conjugated diene units to monovinylarene units of C is between about 0.08 and about 0.26.
26. The monovinylarene-conjugated diene block copolymer of claim 23 , wherein the weight ratio of conjugated diene units to monovinylarene units of C is about 0.2.
27. The monovinylarene-conjugated diene block copolymer of claim 23 , wherein A comprises from about 10 phm to about 40 phm monovinylarene units.
28. The monovinylarene-conjugated diene block copolymer of claim 27 , wherein B comprises from about 10 phm to about 35 phm conjugated diene units.
29. The monovinylarene-conjugated diene block copolymer of claim 23 , in the form of a film having a thickness of about 0.5 mil to about 3 mil and having been oriented at about 70° C., wherein the film has a shrinkage in at least one direction of about 75% at about 100° C.
30. The monovinylarene-conjugated diene block copolymer of claim 29 , wherein the film has a natural shrinkage of less than about 10% after 7 days.
31. The monovinylarene-conjugated diene block copolymer of claim 29 , wherein the film has a haze of less than about 10%.
32. The monovinylarene-conjugated diene block copolymer of claim 29 , wherein the film has a haze of less than about 5%.
33. The monovinylarene-conjugated diene block copolymer of claim 29 , wherein the film has a haze of less than about 3%.