Multiple fiber choppers for molding processes

Details Multiple fiber choppers for molding processes Multiple fiber choppers for molding processes

1999-01-08

2001-02-06

Theisen, Mary Lynn (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Forming articles by uniting randomly associated particles

With liberating or forming of particles

C425S080100, C425S082100, C425S306000

Reexamination Certificate

active

06183675

ABSTRACT:

TECHNICAL FIELD
This invention relates to a process and apparatus for producing fiber-reinforced molded composites. More specifically, this invention relates to the use of multiple fiber choppers therein.
BACKGROUND ART
Fiber choppers are employed in conjunction with liquid resin spray dispensers to form a stream of resin-impregnated chopped fibers that are laid down on a substrate to form a glass fiber reinforced structure. As an elongated glass fiber strand passes between rollers, it is chopped into relatively short fiber segments and propelled by the action of the rollers out through a nozzle opening in the body of the chopper. The body and thus the nozzle are oriented so as to direct the stream of fibers into intersecting relationship with a stream of catalyzed resin, thus forming a stream of resin-impregnated chopped fibers. The stream of resin impregnated fibers is directed toward a substrate, and is allowed to impinge the substrate and form a layer of resin-impregnated fibers on the substrate. Typical products include auto body parts, underground storage tanks and boats.
One industrial application for a chopper is compression molding of interior trim panels for automobile doors. Vinyl panels first are vacuumed formed and transferred to the open mold of a compression mold. A chopper than sprays chopped glass fiber strands onto the vinyl preform. The glass is shaped onto the vinyl preform and followed with a polyol, isocyanate (—NCO) urethane resin mixture. The glass loading and glass spray pattern often cause problems. For example, ribs molded into the panel require high glass loadings of short fibers in the rib area. Edges of the panel require additional glass for added strength. Frequently, a single chopper cannot provide the proper glass loading, glass pattern, glass distribution and the like.
DISCLOSURE OF INVENTION
The process and apparatus of this invention is used with at least two chopper units. The fiber choppers may be laser beam choppers or existing standard chopper units. Our process and apparatus for producing a fiber-reinforced molded composite comprises providing a moldable composition to a molding apparatus, a first fiber chopper providing chopped fibers to the apparatus from a first direction, a second fiber chopper providing chopped fibers to the apparatus from a second direction, wherein the first direction is different from the second direction and molding the moldable composition and fibers in the apparatus under heat and pressure to form the molded composite.
Preferably, the first fiber chopper is on one side of the nozzle spraying resin mixture and the second chopper is on the opposite side of the nozzle, i.e. 180° apart. In another embodiment, a circular chopper surrounding the resin nozzle provides a veil of chopped fibers to the mold.


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