Blends of styrene-butadiene block copolymer with styrenic thermoplastic elastomers for tubing applications
Polymer compositions containing conjugated diene monovinylarene block copolymers and styrenic thermoplastic elastomers are disclosed. These compositions can be used to produce tubing having superior kink resistance properties, and can be a replacement for flexible PVC in various end-use applications, such as in sheet products, film products, tubing products, and adhesive products.
1. A polymer composition comprising:
(a) a conjugated diene monovinylarene block copolymer having from about 55 to about 85 wt. % monovinylarene monomer content, based on the total weight of the copolymer; and
(b) a styrenic thermoplastic elastomer comprising a styrene-butadiene-styrene block copolymer and having from about 22 to about 27 wt. % styrene content, based on the total weight of the styrenic thermoplastic elastomer;
wherein a weight ratio of the conjugated diene monovinylarene block copolymer to the styrenic thermoplastic elastomer is in a range from about 5:95 to about 20:80; and
a kink resistance of tubing produced from the composition and tested in accordance with DIN EN 13868 is in a range from about 8 to about 32 mm.
2. The composition of claim 1 , wherein:
the monovinylarene monomer is styrene; and
the conjugated diene monomer is a butadiene.
3. The composition of claim 1 , wherein a total amount of the conjugated diene monovinylarene block copolymer and the styrenic thermoplastic elastomer is at least about 75 wt. % of the composition.
4. The composition of claim 1 , wherein the styrenic thermoplastic elastomer has about 25 wt. % styrene content, based on the total weight of the styrenic thermoplastic elastomer.
5. An article comprising the composition of claim 1 .
6. A tubing product comprising the composition of claim 1 .
7. The composition of claim 1 , wherein the conjugated diene monovinylarene block copolymer comprises a styrene butadiene block copolymer.
8. The composition of claim 7 , wherein the kink resistance is in a range from about 10 to about 32 mm.
9. The composition of claim 7 , wherein the kink resistance is in a range from about 15 to about 32 mm.
10. An article comprising the composition of claim 9 .
11. The composition of claim 1 , wherein the composition further comprises an additive.
12. The composition of claim 1 , wherein the composition further comprises (c) a third polymer that is different from (a) and (b).
13. The composition of claim 1 , wherein the composition is substantially free of any polymer different from (a) and (b).
14. The composition of claim 1 , wherein the composition has:
a melt flow rate at 200° C. with a 5 Kg load in a range from about 3 to about 20 g/10 min; and
a Shore A hardness in a range from about 50 to about 75.