Improved Impact Modified Polyamide Compositions
Publication Date: 2004-Feb-18
The IP.com Prior Art Database
AbstractMaleic anhydride ("MAH") can be grafted to ethylene styrene interpolymers ("ESI") and provide an improved impact modifier in engineering plastics such as polyamides for various applications.
Maleic anhydride (“MAH”) can be grafted to ethylene styrene interpolymers (“ESI”) and provide an improved impact modifier in engineering plastics such as polyamides for various applications.
It was found that Nylon compounds based on the MAH grafted ESI (“MAH-g-ESI”) show advantages in:
- Impact resistance
- Processability and flow (improved molding cycle)
- Scratch resistance
- Controlled low gloss level desirable for e.g. automotive interior applications
- Heat performance.
Currently, the impact modifiers used in nylons are maleic anhydride grafted polyolefins such as ultra low density polyethylene (“ULDPE’s”) such as or similar to Flexomer DESA 1373 (from Union Carbide Corporation) or maleic anhydride grafted polyolefin elastomer (“POE’s”) such as or similar to Fusabond 494 (from DuPont). Other modifiers can also be used including ionomer polyolefin products such as Surlyn from DuPont. When these modifiers are used to improve the impact of the nylon however, there are limits to the possible attainable balance of impact, flow and heat performance of such compounds.
Ethylene styrene interpolymers used in this study were grafted with maleic anhydride using a reactive extrusion process. The Polymers were extruded on a 58 millimeter (mm) twin screw extruder feeding appropriate amounts of polymer, maleic anhydride and peroxide to the extruder. The conditions and feeds were controlled to allow decomposition of the peroxide initiating the grafting reaction in the extruder at temperatures above 180C. Unreacted maleic anhydride was removed from the polymer melt by a vacuum port at the end of the extruder. Ethylene styrene interpolymers of interest for the grafting process contain more than 5 weight percent (wt %) of styrene, more preferably more than 10 wt %. The grafting level of maleic anhydride of interest for the ethylene styrene interpolymers is more than 0.3 wt %, more preferably more than 0.5wt %. Peroxide level and type was selected such to obtain grafting efficiencies in the reactive extrusion process to be higher than 50% (based on maleic anhydride feed compared to grafted level).
In general these maleic anhydride grafted ethylene styrene interpolymer impact modifiers can be used in the generally known polyamides (nylons) including nylon 6 and nylon 6,6. For providing good levels of impact improvement and good balances of physical properties and processability the maleic anhydride grafted ethylene styrene interpolymer components should be used in amounts of at least about 5 wt %, preferably at least about 10 wt %, more preferably at least about 15 wt % and most preferably at least about 20 wt % to obtain high toughness polyamide compounds. For good balances of properties and cost, the level of maleic anhydride grafted ethylene styrene interpolymer should be less then or equal to about 60 wt %, preferably about 50 wt %, more preferably about 40 wt % and most preferably...