Thermoplastic polyurethane compounds exhibiting stain resistance and enhanced UV stability

Abstract

Thermoplastic articles are molded from thermoplastic polyurethane compounds including blends of aromatic polycaprolactone thermoplastic polyurethane and aliphatic polycaprolactone thermoplastic polyurethane. The thermoplastic articles can have enhanced stability against exposure to ultraviolet (UV) light relative to thermoplastic articles molded from thermoplastic polyurethane compounds including only aromatic polycaprolactone thermoplastic polyurethane as the thermoplastic polyurethane component. Additionally, the thermoplastic articles can have good stain resistance, good clarity (i.e., low haze), and other desirable properties.

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 aliphatic polycaprolactone thermoplastic polyurethane, wherein at least about 50 parts by weight is the aromatic polycaprolactone thermoplastic polyurethane, a secondary polymer in an amount of not more than 200 parts by weight, wherein the secondary polymer is selected from thermoplastic vulcanizates, polyolefin elastomers, copolyesters, and combinations thereof wherein the thermoplastic article, after subjected to QUV Test, achieves a Yellow Index of less than about 8.5: wherein the thermoplastic article is a protective case or portion thereof for a handheld electronic device.

2. The thermoplastic article of claim 1, wherein from about 60 to about 90 parts by weight is the aromatic polycaprolactone thermoplastic polyurethane and from about 10 to about 40 parts by weight is the aliphatic polycaprolactone 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 plasticizer.

5. The thermoplastic article of claim 1, wherein the thermoplastic polyurethane compound is free of other aromatic thermoplastic polyurethane selected from aromatic polyester thermoplastic polyurethane, aromatic polyether thermoplastic polyurethane, and combinations thereof.

6. The thermoplastic article of claim 1, wherein the thermoplastic polyurethane compound is free of other aliphatic thermoplastic polyurethane selected from aliphatic polyester thermoplastic polyurethane, aliphatic polyether thermoplastic polyurethane, and combinations thereof.

7. The thermoplastic article of claim 1: wherein the thermoplastic article, after subjected to QUV Test, achieves (a) a Delta E lower than a comparative Delta E, and (b) a Yellow Index lower than a comparative Yellow Index; wherein a comparative thermoplastic article, after subjected to QUV Test, achieves the comparative Delta E and the comparative Yellow Index, and the comparative thermoplastic article is molded from a comparative thermoplastic polyurethane compound; and wherein the comparative thermoplastic polyurethane compound is identical to the thermoplastic polyurethane compound, except that the comparative thermoplastic polyurethane compound includes 100 parts by weight of thermoplastic polyurethane selected from aromatic polycaprolactone thermoplastic polyurethane.

8. The thermoplastic article of claim 1: wherein the thermoplastic polyurethane compound further comprises from about 0.1 to about 2 parts by weight of ultraviolet light absorber; and wherein the thermoplastic article, after subjected to QUV Test, achieves a Delta E of less than about 5.5 and a Yellow Index of less than about 7.5.

9. The thermoplastic article of claim 1, wherein the thermoplastic article achieves a rating of 1 according to Blue Jean Abrasion Test.

10. An overmolded article comprising: (a) an overmold portion comprising 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 aliphatic polycaprolactone thermoplastic polyurethane, wherein at least about 50 parts by weight is the aromatic polycaprolactone thermoplastic polyurethane, a secondary polymer in an amount of not more than 200 parts by weight, wherein the secondary polymer is selected from thermoplastic vulcanizates, polyolefin elastomers, copolyesters, and combinations thereof; 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; wherein the overmold portion, after subjected to QUV Test, achieves a Yellow Index of less than about 8.5; and wherein the overmolded article is a protective case or portion thereof for a handheld electronic device.

11. A method of improving stability against ultraviolet light exposure by a thermoplastic articlemolded from a thermoplastic polyurethane compound including 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 aliphatic polycaprolactone thermoplastic polyurethane, wherein at least about 50 parts by weight is the aromatic polycaprolactone thermoplastic polyurethane, and a secondary polymer in an amount of not more than 200 parts by weight, wherein the secondary polymer is selected from thermoplastic vulcanizates, polyolefin elastomers, copolyesters, and combinations thereof; and wherein the thermoplastic article, after subjected to QUV Test, achieves Yellow Index of less than about 8.5; and wherein the thermoplastic article is a protective case or portion thereof for a handheld electronic device.

12. The method of claim 11, wherein from about 60 to about 90 parts by weight is the aromatic polycaprolactone thermoplastic polyurethane and from about 10 to about 40 parts by weight is the aliphatic polycaprolactone thermoplastic polyurethane.

13. The method of claim 11: wherein the thermoplastic article, after subjected to QUV Test, achieves (a) a Delta E lower than a comparative Delta E, and (b) a Yellow Index lower than a comparative Yellow Index; wherein a comparative thermoplastic article, after subjected to QUV Test, achieves the comparative Delta E and the comparative Yellow Index, and the comparative thermoplastic article is molded from a comparative thermoplastic polyurethane compound; and wherein the comparative thermoplastic polyurethane compound is identical to the thermoplastic polyurethane compound, except that the comparative thermoplastic polyurethane compound includes 100 parts by weight of thermoplastic polyurethane selected from aromatic polycaprolactone thermoplastic polyurethane.

14. The method of claim 11: wherein the thermoplastic polyurethane compound further includes from about 0.1 to about 2 parts by weight of ultraviolet light absorber; and wherein the thermoplastic article, after subjected to QUV Test, achieves a Delta E of less than about 5.5 and a Yellow Index of less than about 7.5.

15. The method of claim 11, wherein the thermoplastic article achieves a rating of 1 according to Blue Jean Abrasion Test.

Description

EXAMPLES

(1) Non-limiting examples of thermoplastic polyurethane compounds of various embodiments of the disclosed invention are provided.

(2) Table 2 below identifies ingredients and their sources for the thermoplastic polyurethane compounds of the Examples.

(3) TABLE-US-00002 TABLE 2 Ingredient Description Brand Source Aromatic polycaprolactone PEARLTHANE 11T85 Lubrizol TPU Aromatic polycaprolactone ESTANE 2102-90A Lubrizol TPU Aromatic polycaprolactone ESTANE 2102-55D Lubrizol TPU Aliphatic polycaprolactone KRYSTALGRAN Huntsman TPU PN03-221 Aliphatic polycaprolactone ESTANE 91F88EXP Lubrizol TPU Aliphatic polycaprolactone ESTANE ALR Lubrizol TPU CL90-EXP Ultraviolet light absorber TINUVIN 234 BASF Ultraviolet light absorber TINUVIN 622 BASF Mold release wax KEMAMIDE B PMC Biogenix Antioxidant IRGASTAB FS301 BASF

(4) 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.

(5) Table 3 below shows the formulations and certain properties of Comparative Examples A to B and Examples 1 to 2.

(6) TABLE-US-00003 TABLE 3 Example A B 1 2 Ingredients Wt. Parts PEARLTHANE 11T85 100.00 100 85 70 ESTANE 2102-90A — — — — ESTANE 2102-55D — — — — KRYSTALGRAN PN03-221 — — 15 30 ESTANE 91F88EXP — — — — ESTANE ALR CL90-EXP — — — — TINUVIN 234 — 0.6 0.6 0.6 TINUVIN 622 — 0.3 0.3 0.3 KEMAMIDE B 0.1 0.1 0.1 0.1 IRGASTAB FS301 0.15 0.15 0.15 0.15 TOTAL 100.25 101.15 101.15 101.15 Properties Hardness (Shore A) 82 82 78 73 Blue Jean Abrasion Test 1 1 1 1 Clarity (Visual Observation) 1 1 1 1 QUV Test, Delta E 26 6 2.3 1.6 QUV Test, Yellow Index 36 8.7 3.3 2.3

(7) Table 4 below shows the formulations and certain properties of Examples 3 to 6.

(8) TABLE-US-00004 TABLE 4 Example 3 4 5 6 Ingredients Wt. Parts PEARLTHANE 11T85 85 70 85 70 ESTANE 2102-90A — — — — ESTANE 2102-55D — — — — KRYSTALGRAN PN03-221 — — — — ESTANE 91F88EXP 15 30 — — ESTANE ALR CL90-EXP — — 15 30 TINUVIN 234 0.6 0.6 0.6 0.6 TINUVIN 622 0.3 0.3 0.3 0.3 KEMAMIDE B 0.1 0.1 0.1 0.1 IRGASTAB FS301 0.15 0.15 0.15 0.15 TOTAL 101.15 101.15 101.15 101.15 Properties Hardness (Shore A) 81 71 81 77 Blue Jean Abrasion Test 1 1 1 1 Clarity (Visual Observation) 1 1 1 1 QUV Test, Delta E — — — — QUV Test, Yellow Index — — — —

(9) Table 5 below shows the formulations and certain properties of Comparative Example C and Examples 7 to 8.

(10) TABLE-US-00005 TABLE 5 Example C 7 8 Ingredients Wt. Parts PEARLTHANE 11T85 — — — ESTANE 2102-90A 100 85 70 ESTANE 2102-55D — — — KRYSTALGRAN PN03-221 — 15 30 ESTANE 91F88EXP — — — ESTANE ALR CL90-EXP — — — 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 TOTAL 101.15 101.15 101.15 Properties Hardness (Shore A) 90 85 78 Blue Jean Abrasion Test 1 1 1 Clarity (Visual Observation) 1 1 1 QUV Test, Delta E 8.5 4.7 4.6 QUV Test, Yellow Index 12.3 6.8 6.6

(11) Table 6 below shows the formulations and certain properties of Comparative Example D and Examples 9 to 10.

(12) TABLE-US-00006 TABLE 6 Example D 9 10 Ingredients Wt. Parts PEARLTHANE 11T85 — — — ESTANE 2102-90A — — — ESTANE 2102-55D 100 85 70 KRYSTALGRAN PN03-221 15 30 ESTANE 91F88EXP — — — ESTANE ALR CL90-EXP — — — 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 TOTAL 101.15 101.15 101.15 Properties Hardness (Shore A) 91 86 85 Blue Jean Abrasion Test 1 1 1 Clarity (Visual Observation) 1 1 1 QUV Test, Delta E 14.8 5.4 2.6 QUV Test, Yellow Index 21.3 7.9 3.7

(13) 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.

(14) 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.

(15) 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.