THERMOPLASTIC POLYURETHANE COMPOUNDS EXHIBITING ENHANCED STAIN RESISTANCE

Abstract

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.

Claims

1. A thermoplastic article molded from a thermoplastic polyurethane compound, the thermoplastic polyurethane compound comprising: 100 parts by weight of thermoplastic polyurethane selected from blends of 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; and wherein the thermoplastic article achieves a rating of 2 or better according to Blue Jean Abrasion Test.

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, to 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 accessory for an electronic device, the accessory comprising the thermoplastic article of claim 1.

9. The accessory of claim 8, wherein the accessory is a protective case for a handheld electronic device.

10. An overmolded article comprising: (a) on 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.

11. 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 from blends of 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; and wherein the thermoplastic article achieves a rating of 2 or better according to Blue Jean Abrasion Test.

12. The method of claim 11, 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.

13. The method of claim 11, wherein the thermoplastic polyurethane compound is free of aliphatic polyester thermoplastic polyurethane and aliphatic polyether thermoplastic polyurethane.

14. The method of claim 11, wherein the thermoplastic article is an accessory or portion thereof for an electronic device.

15. The method of claim 11, wherein the thermoplastic article is a protective case or portion thereof for a handheld electronic device.

Description

EXAMPLES

[0101] Non-limiting examples of thermoplastic polyurethane compounds of various embodiments of the disclosed invention are provided.

[0102] Table 2 below identifies ingredients and their sources for the thermoplastic polyurethane compounds of the Examples.

TABLE-US-00002 TABLE 2 Ingredient Description Brand Source Aromatic PEARLTHANE 11T85 Lubrizol polycaprolactone TPU Aromatic polyester TPU ELASTOLLAN S85A55N BASF Aromatic polyether TPU IROGRAN A 85 P 4394 UV Huntsman Ultraviolet light absorber TINUVIN 234 BASF Ultraviolet light absorber TINUVIN 622 BASF Mold release wax KEMAMIDE B PMC Biogenix Antioxidant IRGASTAB FS301 BASF Antioxidant IRGANOX 1010 BASF

[0103] To prepare the Examples, the ingredients all together were compounded and extruded as pellets on a twin screw extruder at 196° C. and 300 rpm. Subsequently, the extruded pellets were injection molded (barrel temperature at 205° C. and molder temperature at 25° C.) into specimen plaques having dimensions of 150×125×1.5 mm and evaluated for the reported properties.

[0104] Table 3 below shows the formulations and certain properties of Comparative Examples A to D.

TABLE-US-00003 TABLE 3 Example A B C D Wt. Parts Ingredients PEARLTHANE 11T85 — — — 15 ELASTOLLAN S85A55N 100 — 100 85 IROGRAN A 85 P 4394 UV — 100  — — TINUVIN 234 — — 0.6 0.6 TINUVIN 622 — — 0.3 0.3 KEMAMIDE B 0.1   0.1 0.1 0.1 IRGASTAB FS301 — — 0.15 0.15 IRGANOX 1010 0.2 — — — TOTAL 100.30  100.10 101.15 101.15 Properties Hardness (Shore A) 82 82  81 82 Blue Jean Abrasion Test 3 3 3 3 Clarity (Visual Observation) 1 1 1 1 QUV Test, Delta E — — 16.1 9.7 QUV Test, Yellow Index — — 23.2 14.1

[0105] Table 4 below shows the formulations and certain properties of Comparative Examples A to C.

TABLE-US-00004 TABLE 4 Example 1 2 3 Wt. Parts Ingredients PEARLTHANE 11T85 30 45 60 ELASTOLLAN S85A55N 70 55 40 IROGRAN A 85 P 4394 UV — — — TINUVIN 234 0.6 0.6 0.6 TINUVIN 622 0.3 0.3 0.3 KEMAMIDE B 0.1 0.1 0.1 IRGASTAB FS301 0.15 0.15 0.15 IRGANOX 1010 — — — TOTAL 101.15 101.15 101.15 Properties Hardness (Shore A) 82 83 83 Blue Jean Abrasion Test 2 2 2 Clarity (Visual Observation) 1 1 1 QUV Test, Delta E 8.2 9.4 8.7 QUV Test, Yellow Index 12.1 13.7 12.7

[0106] Without undue experimentation, those having ordinary skill in the art can utilize the written description, including the Examples, to make and use aspects of the disclosed invention.

[0107] All documents cited in the Embodiments of the Invention are incorporated herein by reference in their entirety unless otherwise specified. The citation of any document is not to be construed as an admission that it is prior art with respect to the disclosed invention.

[0108] While particular embodiments of the disclosed invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. The appended claims are intended to cover all such changes and modifications within the scope of the disclosed invention.