Method for preparing fire retardant molding compositions
AssigneeMonsanto Company
InventorsRaymond A. Barkhuff, Jr., William E. Sprenkle, Jr.
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Abstract
Disclosed herein is a method for preparing fire retardant styrenic polymer molding compositions with improved impact strength which compositions contain a metal oxide and a halogenated fire retardant additive. The method comprises dispersing the metal oxide into a minor portion of the styrene polymer component using high intensity mixing and temperatures at or above the fusion temperature of the styrene polymer in order to obtain a uniform dispersion. The metal oxide-polystyrene dispersion is then blended with the other ingredients of the polyblend. The resulting blend is compounded at temperatures greater than 255.degree. C. and then comminuted to form a molding composition.
Claims9
An improved process for compounding fire retardant polystyrene compositions, which comprise a polystyrene component, a metal oxide and a fire retardant halogen additive which method comprises:
- A. mixing the metal oxide with a minor amount of the polystyrene component;
- B. subjecting the mixture to high intensity mixing at or above the fusion temperature of the polystyrene for a time sufficient to uniformly disperse the metal oxide in the molten polystyrene;
- C. comminuting the polystyrene-metal oxide mixture obtained in Step B above;
- D. blending the comminuted polystyrene-metal oxide mixture with the other ingredients of the composition;
- E. compounding the blend from (D) above at temperatures above 255.degree. C. and below the temperature at which degradation occurs;
- and
- F. comminuting the compounded blend.
An improved method for compounding fire retardant polystyrene compositions, which comprise a polystyrene component, antimony oxide and a fire retardant halogen additive which method comprises:
- A. mixing the antimony oxide with a minor amount of the polystyrene component;
- B. subjecting the mixture to high intensity mixing at a temperature in the range of from 160.degree. to 230.degree. C. for a time sufficient to uniformly disperse the antimony oxide in the molten polystyrene;
- C. comminuting the mixture obtained in Step B above;
- D. blending the comminuted polystyrene-antimony oxide mixture with the other ingredients of the composition;
- E. extruding the blend from (D) above at temperatures in the range of from 260.degree. to 290.degree. C.;
- and
- F. comminuting the extruded blend.
Dependencies are inferred from the claim text.