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 selected from the group consisting of: i-A-C-C-C-C-B-CA, i-A-i-C-C-C-C-B-CA, and i-A-i-C-C-C-C-C-B-CA, wherein:
i is a polymerization initiator charge;
A is a monovinylarene charge comprising from about 10 phm to about 40 phm monovinylarene units;
B is a conjugated diene charge comprising from about 5 phm to about 50 phm conjugated diene units;
C is a monovinylarene-conjugated diene charge, each C comprising a weight ratio of conjugated diene units to monovinylarene units from about 0.05 to about 0.33; and
CA is a coupling agent charge.
2. The monovinylarene-conjugated diene block copolymer of claim 1 , wherein the weight ratio of conjugated diene units to monovinylarene units is from about 0.08 to about 0.26.
3. The monovinylarene-conjugated diene block copolymer of claim 1 , wherein:
A comprises from about 15 phm to about 35 phm monovinylarene units; and
B comprises from about 11 phm to about 25 phm conjugated diene units.
4. The monovinylarene-conjugated diene block copolymer of claim 1 , wherein the monovinylarene-conjugated diene block copolymer is formed through the charge order i-A-C-C-C-C-B-CA.
5. The monovinylarene-conjugated diene block copolymer of claim 4 , wherein:
A comprises from about 15 phm to about 35 phm monovinylarene units;
B comprises from about 11 phm to about 25 phm conjugated diene units; and
the weight ratio of conjugated diene units to monovinylarene units is from about 0.06 to about 0.28.
6. The monovinylarene-conjugated diene block copolymer of claim 5 , wherein the monovinylarene-conjugated diene block copolymer is a styrene-butadiene block copolymer.
7. The monovinylarene-conjugated diene block copolymer of claim 1 , wherein the monovinylarene-conjugated diene block copolymer is formed through the charge order i-A-i-C-C-C-C-B-CA.
8. The monovinylarene-conjugated diene block copolymer of claim 7 , wherein:
A comprises from about 15 phm to about 35 phm monovinylarene units;
B comprises from about 11 phm to about 25 phm conjugated diene units; and
the weight ratio of conjugated diene units to monovinylarene units is from about 0.06 to about 0.28.
9. The monovinylarene-conjugated diene block copolymer of claim 8 , wherein the monovinylarene-conjugated diene block copolymer is a styrene-butadiene block copolymer.
10. The monovinylarene-conjugated diene block copolymer of claim 1 , wherein the monovinylarene-conjugated diene block copolymer is formed through the charge order i-A-i-C-C-C-C-C-B-CA.
11. The monovinylarene-conjugated diene block copolymer of claim 10 , wherein:
A comprises from about 15 phm to about 35 phm monovinylarene units;
B comprises from about 11 phm to about 25 phm conjugated diene units; and
the weight ratio of conjugated diene units to monovinylarene units is from about 0.06 to about 0.28.
12. The monovinylarene-conjugated diene block copolymer of claim 11 , wherein the monovinylarene-conjugated diene block copolymer is a styrene-butadiene block copolymer.
13. A shrink film comprising:
(a) from about 5 to about 50 wt. % of a polystyrene; and
(b) a monovinylarene-conjugated diene block copolymer formed through a charge order selected from the group consisting of: i-A-C-C-C-C-B-CA, i-A-i-C-C-C-C-B-CA, and i-A-i-C-C-C-C-C-B-CA, wherein:
i is a polymerization initiator charge;
A is a monovinylarene charge comprising from about 10 phm to about 40 phm monovinylarene units;
B is a conjugated diene charge comprising from about 5 phm to about 50 phm conjugated diene units;
C is a monovinylarene-conjugated diene charge, each C comprising a weight ratio of conjugated diene units to monovinylarene units from about 0.05 to about 0.33; and
CA is a coupling agent charge; and
wherein the shrink film has a thickness in a range from about 0.1 to about 10 mils, a shrinkage in at least one direction of at least about 60% at 100° C., and a haze of less than about 10%.
14. The shrink film of claim 13 , wherein:
A comprises from about 15 phm to about 35 phm monovinylarene units;
B comprises from about 11 phm to about 25 phm conjugated diene units; and
the weight ratio of conjugated diene units to monovinylarene units is from about 0.06 to about 0.28.
15. The shrink film of claim 14 , wherein the monovinylarene-conjugated diene block copolymer is a styrene-butadiene block copolymer.
16. The shrink film of claim 15 , wherein the shrink film has a thickness is a range from about 0.5 to about 3 mils, and a haze of less than about 6%.
17. The shrink film of claim 15 , wherein the shrink film has a shrinkage in at least one direction of at least about 70% at 100° C.
18. The shrink film of claim 13 , wherein the monovinylarene-conjugated diene block copolymer is a styrene-butadiene block copolymer.
19. The shrink film of claim 18 , wherein the monovinylarene-conjugated diene block copolymer is formed through the charge order i-A-C-C-C-C-B-CA.
20. The shrink film of claim 18 , wherein the monovinylarene-conjugated diene block copolymer is formed through the charge order i-A-i-C-C-C-C-B-CA.
21. The shrink film of claim 18 , wherein the monovinylarene-conjugated diene block copolymer is formed through the charge order i-A-i-C-C-C-C-C-B-CA.