Block copolymer composition for overmolding any nylon
View Patent ↗A thermoplastic elastomer (TPE) for overmolding (OM) a nylon substrate with an overmolded layer consists essentially of an inert filler, a plasticizer, preferably a mineral oil, and chosen combinations of ingredients from the following: (i) a functionalized “high rubber” SHDS (styrene-hydrogenated diene-styrene) having a functionality of 1%, the “small end blocks” together present in an amount in the range from about 8-25% by weight; (ii) hydrogenated SDS or SHDS block copolymer having polystyrene endblocks and a polymerized vinyl aromatic monomer in the poly(conjugated diene) midblock, the polystyrene endblocks together present in an amount in the range from 20-30% by weight of the block copolymer, excluding weight of the polystyrene in the polydiene midblock; (iii) a functionalized “high rubber” SHDS having a functionality of >1% but <2%, the “small end blocks” together present in an amount in the range from about 8-25% by weight; (iv) from 0-30% by weight of the composition, of a functionalized polyolefin (F3), the olefin having from 2 to 4 carbon atoms; (v) from 0-15% by wt of the composition, of a hydrogenated nonfunctionalized hydrogenated polystyrene-poly(conjugated diene)-polystyrene (SHDS) block coplymer; and, (vi) an additive to enhance the useful life of the composition.
1. A thermoplastic elastomer (“TPE”) composition for overmolding a predominantly nylon substrate consisting essentially of, an essentially polyamide-free blend of,
(a) an inert filler present in an amount in the range from 5 to 40% by weight of the composition,
(b) from 10-45 parts of a plasticizer per 100 parts of formulated composition, unreactive with an ingredient in the composition, the plasticizer selected from the group consisting of paraffinic oils, olefin oligomers and low Mw polymers;
(c) a block copolymer selected from the group consisting of
(C1), a polystyrene-polydiene-polystyrene block copolymer (SDS rubber), or an at least partially hydrogenated polystyrene-polydiene-polystyrene block copolymer (SHDS rubber), the SDS and SHDS each having “small” polystyrene endblocks, one at each end of a polydiene midblock, which midblock includes a controlled distribution block of polystyrene, the “small” polystyrene endblocks being together present in an amount in the range from about 20% to 30% by weight of the block copolymer, not including the polystyrene in the polydiene midblock, so that (C1) has a weight average molecular weight (“Mw”) high enough to be thermally stable at 282° C. (540° F.),
(C2), a functionalized at least partially hydrogenated “high rubber” SHDS having a functionality of essentially 1%, the “small” endblocks together present in an amount in the range from about 8-25% by weight, and
(C3), a functionalized at least partially hydrogenated SHDS having a functionality of >1% but <2%, in which the end blocks are together present in an amount in the range from >25%-35% by weight;
in any combination, provided that only (C2) may be present by itself, (C1) and (C3) always requiring at least one of the other block copolymers in combination;
(d) from 0-30% by weight of the composition, of a functionalized polyolefin (FP), the olefin having from 2 to 8 carbon atoms;
(e) from 0-15% by wt of the composition, of a hydrogenated nonfunctionalized hydrogenated polystyrene-polydiene-polystyrene (SHDS) block coplymer; and,
(f) an additive to enhance the useful life of the composition.
2. The composition of claim 1 wherein, in (C1), the polymerized vinyl aromatic monomer in the polydiene midblock is polystyrene; the polydiene midblock is selected from hydrogenated polybutadiene, polyisoprene, and poly(isoprene/butadiene); and,
(C1) has a molecular weight Mw in the range from 20,000-400,000.
3. The composition of claim 2 , wherein
(C2) is present in an amount in the range from 5-25% by weight of the composition, and has a molecular weight in the range from 20,000-300,000;
(C3) is present in an amount in the range from 5-25% by weight of the composition and has a molecular weight in the range from 20,000-300,000; and,
plasticizer (b) is present in an amount from 10-40% by weight of the composition.
4. The composition of claim 3 , including from 1-20% of a substantially fully hydrogenated, non-functionalized SDS (“SHDS”).
5. The composition of claim 2 , wherein (C1) and (C3) are absent, and (C2) is present in an amount from 10-40% by weight of the composition.
6. The composition of claim 1 wherein each functionalized SHDS is functionalized with a polar group selected from the group consisting of acid anhydride, carboxyl, carboxylic acid, and amine epoxy.
7. The composition of claim 1 wherein, if the functionalized polyolefin is present, the olefin is selected from ethylene and propylene, and the polyolefin is functionalized with maleic anhydride present in an amount from 0.5-4% of the grafted polymer.
8. A process for the preparation of an article comprising bonding a thermoplastic elastomeric overmolding composition to a nylon substrate, the process comprising, heating a composition according to claim 1 to a temperature in the range from about 182° C.-282° C. (360° F.-540° F.), followed by combining the heated composition with the polar substrate so as to overlie at least a portion of the substrate.
9. An article of arbitrary shape having a layer of the composition of claim 1 molded to at least a portion of the article's surface.