Thermoplastic polyurethane compounds exhibiting enhanced stain resistance
Thermoplastic articles are molded from thermoplastic polyurethane compounds including blends of aromatic polycaprolactone thermoplastic polyurethane and other aromatic thermoplastic polyurethane selected from aromatic polyester thermoplastic polyurethane, aromatic polyether thermoplastic, and combinations thereof. The thermoplastic articles exhibit enhanced stain resistance, as represented by achieving a rating of 2 or better according to Blue Jean Abrasion Test, relative to thermoplastic articles molded from thermoplastic polyurethane compounds including either aromatic polyester thermoplastic polyurethane or aromatic polyether thermoplastic only, while also having good clarity (i.e., low haze) and other desirable properties. The thermoplastic articles can be especially useful as protective cases for handheld electronic devices.
1 . A thermoplastic article molded from a thermoplastic polyurethane compound, the thermoplastic polyurethane compound comprising:
100 parts by weight of thermoplastic polyurethane blend prepared from aromatic polycaprolactone thermoplastic polyurethane and other aromatic thermoplastic polyurethane selected from aromatic polyester thermoplastic polyurethane, aromatic polyether thermoplastic polyurethane, and combinations thereof, wherein from about 20 to about 99 parts by weight is the aromatic polycaprolactone thermoplastic polyurethane and from about 1 to about 80 parts by weight is the other aromatic thermoplastic polyurethane;
wherein the thermoplastic polyurethane compound is free of aliphatic polycaprolactone thermoplastic polyurethane;
wherein the aromatic polycaprolactone thermoplastic polyurethane is a reaction product of reactants consisting of a polycaprolactone polyol and an aromatic diisocyanate and, optionally, chain extender;
wherein the thermoplastic article achieves a rating of 2 or better according to Blue Jean Abrasion Test; and
wherein the thermoplastic article is a protective case for a handheld electronic device.
2 . The thermoplastic article of claim 1 , wherein from about 60 to about 99 parts by weight is the aromatic polycaprolactone thermoplastic polyurethane and from about 1 to about 40 parts by weight is the other aromatic thermoplastic polyurethane.
3 . The thermoplastic article of claim 1 , wherein the thermoplastic polyurethane compound further comprises additives selected from antioxidants and stabilizers; colorants; mold release agents; processing aids; ultraviolet light absorbers; and combinations thereof.
4 . The thermoplastic article of claim 1 , wherein the thermoplastic polyurethane compound further comprises secondary polymer selected from styrenic block copolymers, thermoplastic vulcanizates, polyolefin elastomers, copolyesters, and combinations thereof.
5 . The thermoplastic article of claim 4 , wherein the thermoplastic polyurethane compound further comprises plasticizer.
6 . The thermoplastic article of claim 1 , wherein the thermoplastic polyurethane compound is free of aliphatic polyester thermoplastic polyurethane and aliphatic polyether thermoplastic polyurethane.
7 . The thermoplastic article of claim 1 , wherein the thermoplastic article, after subjected to QUV Test, achieves a Delta E from about 7.5 to about 20 and a Yellow Index from about 11.5 to about 30.
8 . An overmolded article comprising:
(a) overmold portion comprising the thermoplastic article of claim 1 ; and
(b) a substrate portion molded from a thermoplastic resin compound;
wherein the overmold portion is bonded onto the substrate portion at a bond interface, and the bond interface is free of adhesive.
9 . A method of improving resistance to Blue Jean Staining for a thermoplastic article molded from a thermoplastic polyurethane compound comprising 100 parts by weight of thermoplastic polyurethane, the method comprising the step of:
selecting the thermoplastic polyurethane blend prepared from aromatic polycaprolactone thermoplastic polyurethane and other aromatic thermoplastic polyurethane selected from aromatic polyester thermoplastic polyurethane, aromatic polyether thermoplastic polyurethane, and combinations thereof, wherein from about 20 to about 99 parts by weight is the aromatic polycaprolactone thermoplastic polyurethane and from about 1 to about 80 parts by weight is the other aromatic thermoplastic polyurethane;
wherein the thermoplastic polyurethane compound is free of aliphatic polycaprolactone thermoplastic polyurethane;
wherein the aromatic polycaprolactone thermoplastic polyurethane is a reaction product of reactants consisting of a polycaprolactone polyol and an aromatic diisocyanate and, optionally, chain extender;
wherein the thermoplastic article achieves a rating of 2 or better according to Blue Jean Abrasion Test; and
wherein the thermoplastic article is a protective case for a handheld electronic device.
10 . The method of claim 9 , wherein from about 60 to about 99 parts by weight is the aromatic polycaprolactone thermoplastic polyurethane and from about 1 to about 40 parts by weight is the other aromatic thermoplastic polyurethane.
11 . The method of claim 9 , wherein the thermoplastic polyurethane compound is free of aliphatic polyester thermoplastic polyurethane and aliphatic polyether thermoplastic polyurethane.