Thermoplastic elastomer compounds exhibiting superior compression set properties
View Patent ↗A blend of polyisobutylene-based thermoplastic vulcanizate, styrene-ethylene-ethylene-propylene-styrene, low molecular weight liquid polybutene, polyolefin, polyphenylene ether, and, optionally, filler is disclosed which has good processability, lower compression set, and more effective barrier properties for oxygen than the same blend without the styrene-ethylene-ethylene-propylene-styrene and the polyphenylene ether. The blend is superior in oxygen transmission rate properties than a conventional styrenic block copolymer containing thermoplastic elastomer.
1. A thermoplastic elastomer compound, comprising:
(a) thermoplastic vulcanizate (TPV) masterbatch of crosslinked polyisobutylene, polyolefin other than polybutene, and a plasticizer selected from the group consisting of polybutene, paraffin oil, and combinations of them;
(b) styrene ethylene ethylene propylene styrene (SEEPS);
(c) liquid polybutene;
(d) additional polyolefin selected from the group consisting of polyethylene, polypropylene, and both polyethylene and polypropylene;
(e) polyphenylene ether; and
(f) optionally, filler;
wherein the compound has a compression set of less than about 22% when tested at 23° C. for 22 hours using ASTM D395 Test Method B.
2. The compound of claim 1 , wherein the polyisobutylene in the TPV is dynamically crosslinked in the presence of the polyolefin other than polybutene and the plasticizer.
3. The compound of claim 1 , wherein the compound comprises weight percents of ingredients of
PIB-containing TPV
25-60%
SEEPS
8-12%
Liquid Polybutene Plasticizer
15-30%
Polyolefin(s)
5-10%
Polyphenylene Ether
3-8%
Filler
0-35%
Anti-oxidant
0-1%
Other Optional Additives
0-10%
4. The compound of claim 1 , further comprising additives selected from the group consisting of adhesion promoters; biocides (antibacterials, fungicides, and mildewcides), anti-fogging agents; anti-static agents; dispersants; fillers and extenders; fire and flame retardants and smoke suppressants; initiators; lubricants; micas; pigments, colorants and dyes; oils and plasticizers; processing aids; release agents; silanes, titanates and zirconates; slip and anti-blocking agents; stabilizers; stearates; ultraviolet light absorbers; viscosity regulators; waxes; and combinations of them.
5. The compound of claim 1 , wherein the TPV further comprises styrene-isobutylene-styrene (SIBS) in addition to or in replacement of the polyolefin other than polybutene, provided that if the SIBS replaces the polyolefin, then no polybutene or paraffin oil is needed as a plasticizer.
6. The compound of claim 1 , wherein the compound has an oxygen transmission rate of about 6000-8000 cc·mil/m 2 ·day.
7. A molded article, comprising a compound of claim 1 .
8. A method of using the compound of claim 1 , wherein the method comprises the step of molding the compound into an article that has reduced oxygen transmission and lower compression set than a compound which has the same TPV but no SEEPS or polyphenylene ether.