Polysiloxanes in thermoplastic elastomer compounds for overmolded thermoplastic articles

Abstract

An overmolded thermoplastic article includes a substrate portion molded from a thermoplastic resin compound and an overmold portion molded from a thermoplastic elastomer compound. The thermoplastic resin compound includes thermoplastic polymer resin. The thermoplastic elastomer compound includes thermoplastic elastomer and polysiloxane as a mold release agent, and is free of wax. The overmold portion is bonded onto the substrate portion with a peel strength at least comparable to that of an overmolded thermoplastic elastomer compound containing wax as a mold release agent instead of the polysiloxane. Undesirable effects observed with the use of wax as a mold release agent in overmolded thermoplastic elastomer compounds such as blooming and ease of scratching/marring can be reduced, while desirable properties such as silky feel of the surface of the overmold portion and good bonding of the overmold portion onto the substrate portion can be at least maintained.

Claims

1. An overmolded thermoplastic article comprising: a thermoplastic polymer resin substrate portion and an overmold portion molded from a thermoplastic elastomer compound comprising: (a) thermoplastic elastomer and (b) polysiloxane; wherein the thermoplastic elastomer compound is free of wax; wherein the overmold portion is bonded onto the substrate portion at a bond interface, and the bond interface is free of adhesive, and wherein the overmold portion is bonded onto the substrate portion with a peel strength according to ASTM D6862 that is at least about 95% of a control peel strength, wherein the control peel strength is a peel strength according to ASTM D6862 with which a control overmold portion of a control overmolded thermoplastic article is bonded onto a control substrate portion of the control overmolded thermoplastic article; wherein the control overmold portion is molded from a control thermoplastic elastomer compound, and the control thermoplastic elastomer compound is identical to the thermoplastic elastomer except that the polysiloxane is replaced with wax in an amount such that the wax is effective as a mold release agent, wherein the wax comprises erucamide, arachidamide, and behenamide; and wherein the control substrate portion is molded from a control thermoplastic resin compound, and the control thermoplastic resin compound is identical to the thermoplastic polymer resin.

2. The article of claim 1, wherein the overmold portion has a surface, and wherein the polysiloxane is not phase separated from the thermoplastic elastomer compound at the surface.

3. The article of claim 1, wherein the polysiloxane is selected from non-functional polysiloxanes, functional polysiloxanes, and combinations thereof.

4. The article of claim 1, wherein the polysiloxane is a non-functional polysiloxane having a viscosity at 25° C. of about 350 cSt or less, and wherein the polysiloxane is present in an amount ranging from about 0.2 to about 4 weight percent by weight of the thermoplastic elastomer compound.

5. The article of claim 4, wherein the polysiloxane is present in an amount ranging from about 0.5 to about 1.5 weight percent by weight of the thermoplastic elastomer compound.

6. The article of claim 4, wherein the polysiloxane is a non-functional polydimethylsiloxane having a viscosity at 25° C. of about 50 cSt or less.

7. The article of claim 1, wherein the polysiloxane is a functional polysiloxane, and wherein the polysiloxane is present in an amount ranging from about 0.5 to about 5 weight percent by weight of the thermoplastic elastomer compound.

8. The article of claim 7, wherein the polysiloxane is present in an amount ranging from about 0.5 to about 3 weight percent by weight of the thermoplastic elastomer compound.

9. The article of claim 7, wherein the functional polysiloxane is dihydroxypolydimethylsiloxane having a viscosity at 25° C. of about 90 cSt or polyester modified polysiloxane having a melting point of about 54° C.

10. The article of claim 1, wherein the thermoplastic elastomer is selected from the group consisting of styrenic block copolymers (SBC), thermoplastic vulcanizates (TPV), thermoplastic polyolefins (TPO), copolyesters (COPE), thermoplastic polyurethanes (TPU), copolyamides (COPA), olefin block copolymers (OBC), and combinations thereof.

11. The article of claim 1, wherein the thermoplastic elastomer is selected from the group consisting of thermoplastic polyurethanes (TPU), copolyesters (COPE), and combinations thereof, and wherein the thermoplastic elastomer compound is free of styrenic block copolymers (SBC), thermoplastic vulcanizates (TPV), and thermoplastic polyolefins (TPO).

12. The article of claim 1, wherein the thermoplastic elastomer is a blend of a primary thermoplastic elastomer and a secondary bonding agent thermoplastic elastomer, wherein the primary thermoplastic elastomer is selected from styrenic block copolymers (SBC), thermoplastic vulcanizates (TPV), thermoplastic polyolefins (TPO), and combinations thereof, and wherein the secondary bonding agent thermoplastic elastomer is selected from thermoplastic polyurethanes (TPU), copolyesters (COPE), and combinations thereof.

13. The article of claim 10, wherein the styrenic block copolymer is selected from the group consisting of styrene-ethylene/butylene-styrene (SEBS) block copolymer, styrene-ethylene/propylene-styrene (SEPS) block copolymer, styrene-ethylene/ethyl ene/propylene-styrene (SEEPS) block copolymer, styrene-isobutylene-styrene (SIBS) block copolymer, styrene-butadiene-styrene (SBS) block copolymer, styrene-isoprene-styrene (SIS) block copolymer, and combinations thereof.

14. The article of claim 1, wherein the thermoplastic elastomer is present in an amount ranging from about 85 to about 99.8 weight percent by weight of the thermoplastic elastomer compound.

15. The article of claim 1, wherein the thermoplastic elastomer compound further comprises one or more additives selected from the group consisting of antioxidants and stabilizers; blowing and foaming agents; colorants; flame retardants and smoke suppressants; fillers; impact modifiers; plasticizers; ultraviolet light absorbers; and combinations thereof.

16. The article of claim 1, wherein the thermoplastic elastomer compound has a Shore A hardness no greater than about 90 according to ASTM D2240.

17. The article of claim 1, wherein the thermoplastic elastomer compound has a Shore A hardness of about 78 according to ASTM D2240, and wherein the overmold portion is bonded onto the substrate portion with a peel strength of at least about 40 pounds per linear inch according to ASTM D6862.

18. The article of claim 1, wherein the thermoplastic polymer resin is a thermoplastic engineering resin selected from the group consisting of polycarbonates, acrylonitrile butadiene styrenes, polyamides, polystyrenes, polyesters, polyoxymethylenes, polyphenylene oxides, and alloys or blends thereof.

19. A method of making an overmolded thermoplastic article having a substrate portion and an overmold portion, the method comprising the steps of: (a) providing a thermoplastic polymer resin; (b) providing a thermoplastic elastomer compound comprising (i) thermoplastic elastomer and (ii) polysiloxane, and wherein the thermoplastic elastomer compound is free of wax; (c) molding the thermoplastic polymer resin to provide the substrate portion; and (d) overmolding the thermoplastic elastomer compound to provide the overmold portion, wherein the overmold portion is bonded onto the substrate portion at a bond interface, and wherein the bond interface is free of adhesive, thereby providing the overmolded thermoplastic article, and wherein the overmold portion is bonded onto the substrate portion with a peel strength according to ASTM D6862 that is at least about 95% of a control peel strength, wherein the control peel strength is a peel strength according to ASTM D6862 with which a control overmold portion of a control overmolded thermoplastic article is bonded onto a control substrate portion of the control overmolded thermoplastic article; wherein the control overmold portion is molded from a control thermoplastic elastomer compound, and the control thermoplastic elastomer compound is identical to the thermoplastic elastomer except that the polysiloxane is replaced with a wax in an amount such that the wax is effective as a mold release agent, wherein the wax comprises erucamide, arachidamide, and behenamide; and wherein the control substrate portion is a control thermoplastic polymer resin, and the control thermoplastic polymer resin is identical to the thermoplastic polymer resin.

20. An overmolded thermoplastic article comprising: a thermoplastic polymer resin substrate portion; and an overmold portion molded from a thermoplastic elastomer compound comprising: (a) thermoplastic elastomer; and (b) polysiloxane; wherein the thermoplastic elastomer compound is free of wax; the overmold portion is bonded onto the substrate portion at a bond interface, and the bond interface is free of adhesive; and the polysiloxane is a non-functional polysiloxane having a viscosity at 25 ° C. of about 50 cSt or less, and the polysiloxane is present in an amount ranging from about 0.2 to about 4 weight percent by weight of the thermoplastic elastomer compound.

21. An overmolded thermoplastic article comprising: a substrate portion molded from a thermoplastic resin compound comprising thermoplastic polymer resin; and an overmold portion molded from a thermoplastic elastomer compound comprising: (a) thermoplastic elastomer; and (b) polysiloxane; wherein the thermoplastic elastomer compound is free of wax; the overmold portion is bonded onto the substrate portion at a bond interface, and the bond interface is free of adhesive; and the polysiloxane is a functional polysiloxane, and wherein the polysiloxane is present in an amount ranging from about 0.5 to about 5 weight percent by weight of the thermoplastic elastomer compound and the functional polysiloxane is dihydroxypolydimethylsiloxane having a viscosity at 25° C. of about 90 cSt or polyester modified polysiloxane having a melting point of about 54° C.

Description

EXAMPLES

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

(2) Table 2 below shows sources of ingredients for the thermoplastic elastomer compounds of Examples 1 to 14 and Comparative Examples A to E.

(3) TABLE-US-00002 TABLE 2 Ingredient Description Brand Source Styrene-(ethylene/butylene)- KRATON A1535 Kraton styrene block copolymer Polymers White oil 380 vis oil Multiple Thermoplastic polyurethane IROGRAN A85A Huntsman 4394 UV Color concentrate CC10190262X0 black PolyOne Antioxidant IRGANOX 1010 BASF Antioxidant IRGAFOS 168 BASF Wax KEMAMIDE E PMC Biogenix Wax KEMAMIDE B PMC Biogenix Polydimethylsiloxane XIAMETER PMX-200, Dow Corning 50 CS Polydimethylsiloxane XIAMETER PMX-200, Dow Corning 350 CS Dihydroxypolydimethyl- TEGOMER H-Si 2315 Evonik siloxane Polyester modified siloxane TEGOMER H-Si 6441 P Evonik Polycarbonate LEXAN 141R Sabic

(4) Examples of the thermoplastic elastomer compound were compounded and extruded as pellets on a twin extruder at a temperature of 360° F. and a mixing speed of 400 rpm. Subsequently, test specimen plaques were prepared by injection molding and then evaluated for the reported properties.

(5) Shore A hardness was assessed according to ASTM D2240.

(6) Blooming/phase separation was assessed by visual observation of the surface of the test specimen.

(7) Finger nail scratch was assessed by visual observation after the surface of the test specimen was manually scratched with a human finger nail.

(8) Overmolding (OM) peel force was assessed according to ASTM D6862. Test specimens were prepared by overmolding the exemplified thermoplastic elastomer compound onto a substrate of polycarbonate (LEXAN 141R brand available from Sabic) to provide the test specimen.

(9) Table 3 below shows the formulations and certain properties of Comparative Example A.

(10) TABLE-US-00003 TABLE 3 Example A Wt. Wt. Parts % Ingredient KRATON A1535 40 6.06 380 vis oil 26 3.94 IROGRAN A85A 4394 UV 584 88.43 CC10190262X0 black 6.7 1.01 IRGANOX 1010 1 0.15 IRGAFOS 168 0.7 0.11 KEMAMIDE E 1 0.15 KEMAMIDE B 1 0.15 XIAMETER PMX-200, 50 CS — — XIAMETER PMX-200, 350 CS — — TEGOMER H-Si 2315 — — TEGOMER H-Si 6441 P — — TOTAL 660.4 100.00 Properties Hardness (Shore A) 78 (ASTM D2240) Blooming/Phase Separation No Finger Nail Scratch Yes OM Peel Force (pli) 45 (ASTM D6862)

(11) Table 4 below shows the formulations and certain properties of Examples 1 to 3 and Comparative Examples B to C.

(12) TABLE-US-00004 TABLE 4 Example 1 2 3 Wt. Wt. Wt. Wt. Wt. Wt. Parts % Parts % Parts % Ingredient KRATON A1535 40 6.04 40 6.01 40 5.98 380 vis oil 26 3.93 26 3.91 26 3.89 IROGRAN A85A 4394 UV 584 88.24 584 87.81 584 87.37 CC10190262X0 black 6.7 1.01 6.7 1.01 6.7 1.00 IRGANOX 1010 1 0.15 1 0.15 1 0.15 IRGAFOS 168 0.7 0.11 0.7 0.11 0.7 0.10 KEMAMIDE E — — — — — — KEMAMIDE B — — — — — — XIAMETER PMX-200, 50 CS 3.4 0.51 6.7 1.01 10 1.50 XIAMETER PMX-200, 350 CS — — — — — — TEGOMER H-Si 2315 — — — — — — TEGOMER H-Si 6441 P — — — — — — TOTAL 661.8 100.00 665.1 100.00 668.4 100.00 Properties Hardness (Shore A) 78 78 78 (ASTM D2240) Blooming/Phase No No No Separation Finger Nail No No No Scratch OM Peel Force (pli) 45 45 43 (ASTM D6862) Example B C Wt. Wt. Wt. Wt. Parts % Parts % Ingredient KRATON A1535 40 5.95 40 5.89 380 vis oil 26 3.87 26 3.83 IROGRAN A85A 4394 UV 584 86.93 584 86.02 CC10190262X0 black 6.7 1.00 6.7 0.99 IRGANOX 1010 1 0.15 1 0.15 IRGAFOS 168 0.7 0.10 0.7 0.10 KEMAMIDE E — — — — KEMAMIDE B — — — — XIAMETER PMX-200, 50 CS 13.4 1.99 20.5 3.02 XIAMETER PMX-200, 350 CS — — — — TEGOMER H-Si 2315 — — — — TEGOMER H-Si 6441 P — — — — TOTAL 671.8 100.00 678.9 100.00 Properties Hardness (Shore A) 78 78 (ASTM D2240) Blooming/Phase No Yes Separation Finger Nail No No Scratch OM Peel Force (pli) 38 28 (ASTM D6862)

(13) Table 5 below shows the formulations and certain properties of Examples 4 to 6 and Comparative Examples D to E.

(14) TABLE-US-00005 TABLE 5 Example 4 5 6 Wt. Wt. Wt. Wt. Wt. Wt. Parts % Parts % Parts % Ingredient KRATON A1535 40 6.04 40 6.01 40 5.98 380 vis oil 26 3.93 26 3.91 26 3.89 IROGRAN A85A 4394 UV 584 88.24 584 87.81 584 87.37 CC10190262X0 black 6.7 1.01 6.7 1.01 6.7 1.00 IRGANOX 1010 1 0.15 1 0.15 1 0.15 IRGAFOS 168 0.7 0.11 0.7 0.11 0.7 0.10 KEMAMIDE E — — — — — — KEMAMIDE B — — — — — — XIAMETER PMX-200, 50 CS — — — — — — XIAMETER PMX-200, 350 CS 3.4 0.51 6.7 1.01 10 1.50 TEGOMER H-Si 2315 — — — — — — TEGOMER H-Si 6441 P — — — — — — TOTAL 661.8 100.00 665.1 100.00 668.4 100.00 Properties Hardness (Shore A) 78 78 78 (ASTM D2240) Blooming/Phase No No No Separation Finger Nail No No No Scratch OM Peel Force (pli) 45 45 45 (ASTM D6862) Example D E Wt. Wt. Wt. Wt. Parts % Parts % Ingredient KRATON A1535 40 5.95 40 5.89 380 vis oil 26 3.87 26 3.83 IROGRAN A85A 4394 UV 584 86.93 584 86.02 CC10190262X0 black 6.7 1.00 6.7 0.99 IRGANOX 1010 1 0.15 1 0.15 IRGAFOS 168 0.7 0.10 0.7 0.10 KEMAMIDE E — — — — KEMAMIDE B — — — — XIAMETER PMX-200, 50 CS — — — — XIAMETER PMX-200, 350 CS 13.4 1.99 20.5 3.02 TEGOMER H-Si 2315 — — — — TEGOMER H-Si 6441 P — — — — TOTAL 671.8 100.00 678.9 100.00 Properties Hardness (Shore A) 78 78 (ASTM D2240) Blooming/Phase Yes Yes Separation Finger Nail No No Scratch OM Peel Force (pli) 45 45 (ASTM D6862)

(15) Table 6 below shows the formulations and certain properties of Examples 7 to 11.

(16) TABLE-US-00006 TABLE 6 Example 7 8 9 Wt. Wt. Wt. Wt. Wt. Wt. Parts % Parts % Parts % Ingredient KRATON A1535 40 6.04 40 6.01 40 5.98 380 vis oil 26 3.93 26 3.91 26 3.89 IROGRAN A85A 4394 UV 584 88.24 584 87.81 584 87.37 CC10190262X0 black 6.7 1.01 6.7 1.01 6.7 1.00 IRGANOX 1010 1 0.15 1 0.15 1 0.15 IRGAFOS 168 0.7 0.11 0.7 0.11 0.7 0.10 KEMAMIDE E — — — — — — KEMAMIDE B — — — — — — XIAMETER PMX-200, 50 CS — — — — — — XIAMETER PMX-200, 350 CS — — — — — — TEGOMER H-Si 2315 3.4 0.51 6.7 1.01 10 1.50 TEGOMER H-Si 6441 P — — — — — — TOTAL 661.8 100.00 665.1 100.00 668.4 100.00 Properties Hardness (Shore A) 78 78 78 (ASTM D2240) Blooming/Phase No No No Separation Finger Nail No No No Scratch OM Peel Force (pli) 40 45 40 (ASTM D6862) Example 10 11 Wt. Wt. Wt. Wt. Parts % Parts % Ingredient KRATON A1535 40 5.95 40 5.89 380 vis oil 26 3.87 26 3.83 IROGRAN A85A 4394 UV 584 86.93 584 86.02 CC10190262X0 black 6.7 1.00 6.7 0.99 IRGANOX 1010 1 0.15 1 0.15 IRGAFOS 168 0.7 0.10 0.7 0.10 KEMAMIDE E — — — — KEMAMIDE B — — — — XIAMETER PMX-200, 50 CS — — — — XIAMETER PMX-200, 350 CS — — — — TEGOMER H-Si 2315 13.4 1.99 20.5 3.02 TEGOMER H-Si 6441 P — — — — TOTAL 671.8 100.00 678.9 100.00 Properties Hardness (Shore A) 78 78 (ASTM D2240) Blooming/Phase No No Separation Finger Nail No No Scratch OM Peel Force (pli) 40 40 (ASTM D6862)

(17) Table 7 below shows the formulations and certain properties of Examples 12 to 14.

(18) TABLE-US-00007 TABLE 7 Example 12 13 14 Wt. Wt. Wt. Wt. Wt. Wt. Parts % Parts % Parts % Ingredient KRATON A1535 40 6.04 40 5.98 40 5.89 380 vis oil 26 3.93 26 3.89 26 3.83 IROGRAN A85A 4394 UV 584 88.24 584 87.37 584 86.02 CC10190262X0 black 6.7 1.01 6.7 1.00 6.7 0.99 IRGANOX 1010 1 0.15 1 0.15 1 0.15 IRGAFOS 168 0.7 0.11 0.7 0.10 0.7 0.10 KEMAMIDE E — — — — — — KEMAMIDE B — — — — — — XIAMETER PMX-200, 50 CS — — — — — — XIAMETER PMX-200, 350 CS — — — — — — TEGOMER H-Si 2315 — — — — — — TEGOMER H-Si 6441 P 3.4 0.51 10 1.50 20.5 3.02 TOTAL 661.8 100.00 668.4 100.00 678.9 100.00 Properties Hardness (Shore A) 78 78 78 (ASTM D2240) Blooming/Phase No No No Separation Finger Nail No No No Scratch OM Peel Force (pli) 43 43 43 (ASTM D6862)

(19) Without undue experimentation, those having ordinary skill in the art can utilize the written description, including the Examples, to make and use overmolded thermoplastic articles according to the present invention.

(20) 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 present invention.

(21) While particular embodiments of the present 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. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of the present invention.