Polymer composition and uses thereof

1. A polymer composition, comprising:

a block copolymer (a) comprising a polymer block A, which comprises mainly an α-methylstyrene, and a hydrogenated or unhydrogenated polymer block B, which comprises a conjugated diene, wherein block copolymer (a) has a weight average molecular weight of 30,000 to 200,000;

an acrylic resin (b) which is a homopolymer of methyl methacrylate or a copolymer comprising methyl methacrylate as the major component and copolymerizable monomers selected from the group consisting of (meth)acrylic acid, metal salts of (meth)acrylic acid, (meth)acrylic acid esters, vinyl acetate, aromatic vinyl compounds, maleic anhydride, maleimide compounds and mixtures thereof; and

optionally, a softener (c); and

wherein proportions (by mass) of respective components in the polymer composition are such that each of the following relationships (1) and (2) holds:

0.05 <Wb/Wa <2  (1) and

Wc /( Wa+Wb+Wc )<0.5  (2)

wherein Wa, Wb, and Wc represent the amounts (by mass) of the block copolymer (a), the acrylic resin (b) and the softener (c), respectively, and

wherein the polymer composition has a morphology in which the block copolymer (a) forms a continuous phase (matrix) and the acrylic resin (b) forms particles having an average particle size of 0.2 μm or less, that are dispersed throughout the continuous phase, forming sea-island structures.

2. The polymer composition according to claim 1 , wherein the block copolymer (a) comprises:

(1) a polymer block A comprising mainly an α-methylstyrene and having a weight average molecular weight of 1,000 to 50,000; and

(2) a polymer block B including a block b1 that has a weight average molecular weight of 1,000 to 30,000, and in which less than 30% of the conjugated diene units to constitute the block are linked via 1,4-linkages, and a block b2 that has a weight average molecular weight of 25,000 to 190,000, and in which 30% or more of the conjugated diene units to constitute the block are linked via 1,4-linkages; and

wherein the block copolymer (a) includes at least one A-b1-b2 structure.

3. A stretchable material, comprising:

the polymer composition according to claim 1 .

4. The stretchable material according to claim 3 , wherein the stretchable material is provided in the form of a film, strand, band, or nonwoven fabric comprising the polymer composition.

5. The stretchable material according to claim 3 , wherein the stretchable material yields a 0.8 MPa or larger stress when formed into a 1 mm thick, No.2 dumbbell-molded sample piece, according to JIS K 6251, and stretched by 50% at a test speed of 20 mm/min at 25° C., with the grip distance of 70 mm, and gives a 50% or higher stress retention after held under the conditions for 2 hours.

6. A laminate, comprising:

a layer comprising the polymer composition according to claim 1 , and

a layer comprising a different material.

7. The laminate according to claim 6 , wherein the different material is a thermoplastic resin.

8. The laminate according to claim 7 , wherein the different material comprises at least one thermoplastic resin selected from the group consisting of olefin-based resin, olefin-based thermoplastic elastomer, styrene-based thermoplastic elastomer, and a resin composition containing a styrene-based thermoplastic elastomer.

9. A laminate, comprising:

an outermost layer comprising the polymer composition according to claim 1 , and

a layer comprising a different material.

10. A foam composition, comprising:

the polymer composition according to claim 1 , and

a blowing agent (d), and wherein the blowing agent (d) is contained in a proportion (by mass), such that the following relationship (3) holds:

0.01 <Wd /( Wa+Wb+Wc )<0.1  (3)

wherein Wa, Wb, Wc, and Wd represent the amounts (by mass) of the block copolymer (a), the acrylic resin (b), the softener (c), and the blowing agent (d) that together form the foam composition, respectively.

11. A foam obtained by foaming the foam composition according to claim 10 .

12. A stretchable material, comprising:

the polymer composition according to claim 2 .

13. A laminate, comprising:

a layer comprising the polymer composition according to claim 2 , and

a layer comprising a different material.

14. A laminate, comprising:

an outermost layer comprising the polymer composition according to claim 2 , and

a layer comprising a different material.

15. A foam composition, comprising:

the polymer composition according to claim 2 , and a blowing agent (d), and wherein the blowing agent (d) is contained in a proportion (by mass), such that the following relationship (3) holds:

0.01 <Wd /( Wa+Wb+Wc )<0.1  (3)

wherein Wa, Wb, Wc, and Wd represent the amounts (by mass) of the block copolymer (a), the acrylic resin (b), the softener (c), and the blowing agent (d) that together form the foam composition, respectively.

16. The polymer composition according to claim 1 , wherein the acrylic resin (b) is a copolymer comprising methyl methacrylate and methyl acrylate.

17. The polymer composition according to claim 2 , wherein the acrylic resin (b) is a copolymer comprising methyl methacrylate and methyl acrylate.