Overmolding thermoplastic elastomer compounds having high bio-based content
Thermoplastic elastomer compounds include (a) hydrogenated styrene-farnesene-styrene block copolymer, (b) thermoplastic polyester elastomer having a bio-based content of at least about 45%, (c) polyolefin having a bio-based content of at least about 95%, (d) secondary styrenic block copolymer such as styrene-ethylene/butylene-styrene block copolymer, and (e) plasticizer. The thermoplastic elastomer compounds have a bio-based content of at least about 40%. Additionally, the thermoplastic elastomer compounds have an adhesion of at least about 10 pli according to a 90° Peel Test on at least one of acrylonitrile butadiene styrene, polycarbonate/acrylonitrile butadiene styrene, and polycarbonate. The thermoplastic elastomer compounds can be especially useful for making overmolded thermoplastic articles.
1. A thermoplastic elastomer compound comprising:
(a) from about 10 to about 65 weight percent, by weight of the compound, of a hydrogenated styrene-farnesene-styrene block copolymer;
(b) from about 10 to about 65 weight percent, by weight of the compound, of a thermoplastic polyester elastomer having a bio-based content of at least about 45%;
(c) from about 2 to about 20 weight percent, by weight of the compound, of a polyolefin having a bio-based content of at least about 95%;
(d) from about 2 to about 20 weight percent, by weight of the compound, of a secondary styrenic block copolymer;
(e) from about 2 to about 20 weight percent, by weight of the compound, of a plasticizer;
(f) from 0 to about 15 weight percent, by weight of the compound, of a hydrocarbon resin; and
(g) from 0 to about 10 weight percent, by weight of the compound, of one or more additives selected from the group consisting of antioxidants; colorants; ultraviolet light absorbers; waxes; and combinations thereof;
wherein the compound has a bio-based content of at least about 40%; and
wherein the compound has an adhesion of at least about 10 pli according to a 90° Peel Test on at least one of acrylonitrile butadiene styrene, polycarbonate/acrylonitrile butadiene styrene, and polycarbonate.
2. The compound of claim 1 , wherein the compound has a bio-based content of at least about 50%.
3. The compound of claim 1 , wherein the compound has an adhesion of at least about 10 pli according to a 90° Peel Test on each of acrylonitrile butadiene styrene (ABS), polycarbonate/acrylonitrile butadiene styrene (PC/ABS), and polycarbonate (PC).
4. The compound of claim 1 , wherein the secondary styrenic block copolymer is selected from styrene-ethylene/butylene-styrene (SEBS) block copolymer, styrene-ethylene/propylene-styrene (SEPS) block copolymer, styrene-ethylene/ethylene/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.
5. The compound of claim 1 , wherein the compound includes from about 2 to about 10 weight percent, by weight of the compound, of the hydrocarbon resin.
6. The compound of claim 1 , wherein the compound further comprises two or more additives selected from the group consisting of antioxidants; colorants; ultraviolet light absorbers; waxes; and combinations thereof.
7. The compound of claim 1 , wherein the hydrogenated styrene-farnesene-styrene block copolymer and the thermoplastic polyester elastomer are present at a weight ratio ranging from about 1:2 to about 2:1.
8. The compound of claim 1 , wherein the hydrogenated styrene-farnesene-styrene block copolymer comprises a combination of a first grade of hydrogenated styrene-farnesene-styrene block copolymer and a second grade of hydrogenated styrene-farnesene-styrene block copolymer, wherein the first grade of hydrogenated styrene-farnesene-styrene block copolymer has a first melt flow rate and a first hardness and the second grade of hydrogenated styrene-farnesene-styrene block copolymer has a second melt flow rate different from the first melt flow rate and a second hardness different from the first hardness.
9. The compound of claim 8 , wherein the first grade of hydrogenated styrene-farnesene-styrene block copolymer and the second grade of hydrogenated styrene-farnesene-styrene block copolymer are present at a weight ratio ranging from about 1:3 to about 3:1.
10. A thermoplastic article molded from the thermoplastic elastomer compound of claim 1 .
11. An overmolded thermoplastic article comprising:
(a) an overmold portion molded from the thermoplastic elastomer compound of claim 1 ; and
(b) a substrate portion molded from a thermoplastic resin compound comprising thermoplastic resin selected from the group consisting of acrylonitrile butadiene styrene (ABS), polycarbonate/acrylonitrile butadiene styrene (PC/ABS), and polycarbonate (PC);
wherein the overmold portion is bonded onto the substrate portion at a bond interface, and the bond interface is free of adhesive.
12. A method of making an overmolded thermoplastic article having a substrate portion and an overmold portion, the method comprising the steps of:
(a) providing the thermoplastic elastomer compound of claim 1 ;
(b) providing a thermoplastic resin compound comprising thermoplastic resin selected from the group consisting of acrylonitrile butadiene styrene, polycarbonate/acrylonitrile butadiene styrene, and polycarbonate;
(c) molding the thermoplastic resin compound 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.