Transparent thermoplastic resin composition having improved whitening resistance at low temperature and excellent impact strength

1. A transparent thermoplastic resin composition that can have improved whitening resistance at low temperatures comprising:

(A) a rubber-modified graft copolymer which is prepared by copolymerizing (a2) a (meth)acrylic acid alkyl ester monomer, (a3) a styrene-based monomer and (a4) an acrylonitrile-based monomer onto (a1) a butadiene-based rubber polymer;

(B) a styrene-based copolymer having glass transition temperature of about 90 to about 100° C. which is prepared by copolymerizing (b1) a methacrylic acid alkyl ester monomer, (b2) an acrylic acid alkyl ester monomer, (b3) a styrene-based monomer and (b4) an acrylonitrile-based monomer; and

(C) a silicone oil.

2. The transparent thermoplastic resin composition of claim 1 , wherein the difference between the refractive index of the rubber-modified graft copolymer (A) and the refractive index of the butadiene-based rubber polymer (a1) is about 0.005 or less, and the difference between the refractive index of the rubber-modified graft copolymer (A) and the refractive index of the styrene-based copolymer (B) is about 0.005 or less.

3. The transparent thermoplastic resin composition of claim 1 , wherein the transparent thermoplastic resin composition comprises about 5 to about 75% by weight of the rubber-modified graft copolymer (A); about 25 to about 95% by weight of the styrene-based copolymer (B); and about 0.01 to about 0.1 parts by weight of the silicone oil (C) based on about 100 parts by weight of the rubber-modified graft copolymer (A) and the styrene-based copolymer (B).

4. The transparent thermoplastic resin composition of claim 1 , wherein the rubber-modified graft copolymer (A) is prepared by copolymerizing the (meth)acrylic acid alkyl ester monomer (a2), the styrene-based monomer (a3) and the acrylonitrile-based monomer (a4) at about 55 to about 80 grafting percent onto the butadiene-based rubber polymer (a1).

5. The transparent thermoplastic resin composition of claim 1 , wherein the rubber-modified graft copolymer (A) comprises about 20 to about 60% by weight of the butadiene-based rubber polymer (a1), about 20 to about 60% by weight of the (meth)acrylic acid alkyl ester monomer (a2), about 10 to about 40% by weight of the styrene-based monomer (a3) and about 1 to about 20% by weight of the acrylonitrile-based monomer (a4).

6. The transparent thermoplastic resin composition of claim 1 , wherein the styrene-based copolymer (B) comprises about 40 to about 80% by weight of the methacrylic acid alkyl ester monomer (b1), about 5 to about 50% by weight of the acrylic acid alkyl ester monomer (b2), about 1 to about 30% by weight of the styrene-based monomer (b3) and about 1 to about 20% by weight of the acrylonitrile-based monomer (b4).

7. The transparent thermoplastic resin composition of claim 1 , wherein the transparent thermoplastic resin composition further comprises methyl methacrylate-styrene-acrylonitrile (MSAN) copolymer.

8. The transparent thermoplastic resin composition of claim 1 , wherein the butadiene-based rubber polymer (a1) comprises polybutadiene polymer, styrene-butadiene copolymer or a combination thereof.

9. The transparent thermoplastic resin composition of claim 1 , wherein the butadiene-based rubber polymer (a1) has an average particle diameter of about 0.05 to about 0.4 μm, about 60 to about 95% by weight of gel content, and a swelling index of about 10 to about 30.

10. The transparent thermoplastic resin composition of claim 1 , wherein the (meth)acrylic acid alkyl ester monomer (a1) has 2 to 20 carbon atoms, the methacrylic acid alkyl ester monomer (b1) has 2 to 20 carbon atoms, and the acrylic acid alkyl ester monomer (b2) has 2 to 20 carbon atoms.

11. The transparent thermoplastic resin composition of claim 1 , wherein the styrene-based monomer comprises styrene, α-ethyl styrene, α-methyl styrene, p-methyl styrene, o-t-butyl styrene, bromo styrene, chloro styrene, trichloro styrene or a combination thereof.

12. The transparent thermoplastic resin composition of claim 1 , wherein the acrylonitrile-based monomer comprises acrylonitrile, methacrylonitrile, fumaronitrile or a combination thereof.

13. The transparent thermoplastic resin composition of claim 1 , wherein the styrene-based copolymer (B) has a weight average molecular weight of about 100,000 to about 130,000 g/mol.

14. The transparent thermoplastic resin composition claim 1 , further comprising one or more additives selected from the group consisting of polymerization initiators, catalysts for initiation, emulsifying agents, molecular weight control agents, heat stabilizers, release agents, dispersants, anti-dripping agents, UV stabilizers, inorganic fillers, inorganic fibers, and combinations thereof.

15. A molded article prepared from the transparent thermoplastic resin composition of claim 1 .

16. The molded article of claim 15 , wherein the molded article has an Izod impact strength (un-notched) of about 8 to about 20 kgf·cm/cm measured for a ⅛ inch thickness in accordance with ASTM D256.

17. The molded article of claim 15 , wherein the molded article has a haze value of about 1.5 to about 4.0% measured for a 3.2 mm thickness in accordance with ASTM D1003.