Plastic article or earthenware shaping or treating: apparatus – Distinct means to feed – support or manipulate preform stock... – And means to form or reshape preform
Reexamination Certificate
1998-11-12
2001-04-10
Weisberger, Richard (Department: 1774)
Plastic article or earthenware shaping or treating: apparatus
Distinct means to feed, support or manipulate preform stock...
And means to form or reshape preform
C425S110000, C425S122000, C425S465000
Reexamination Certificate
active
06213746
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a die and a process of reinforcing a resin with fibers. More particularly, the invention relates to a die and a process of splaying fibers to homogeneously impregnate the fibers with molten resin.
BACKGROUND OF THE INVENTION
Resins such as thermoplastic materials may be used in various applications. For applications in which external forces are exerted on a resin structure, it is desirable that the resin structure be reinforced with fibers such as fiberglass. Reinforcing a resin structure in this way desirably increases the resistance of the resin structure to such external forces. Moreover, fiber reinforcement of resin is beneficial because it more easily allows the resin to be cut and formed into pellets or other similar structures after the resin solidifies.
A conventional scheme for reinforcing a resin with fibers generally entails drawing a continuous bundle or roving of fibers into a molded die, wetting the fibers with molten resin within the die, extruding the wetted fibers from the die, and cooling the extruded fibers to form solidified and reinforced resin structures. These resin structures may then be cut into pellets of desired size for any of various uses, including injection molding. Other more specific uses are described in U.S. Pat. No. 5,268,050, which is incorporated herein by reference.
When a roving of fibers is wetted with molten resin, it is desirable that the molten resin uniformly impregnate the fibers in the roving. That is, not only should the molten resin coat the external surface of the roving, but the resin should also be evenly distributed and interspersed between individual fibers in the roving. Uniform impregnation maximizes reinforcement of the resin structure and yields the most desirable physical properties of such structure. If uniform impregnation is not achieved during the wetting stage, it is likely that fibers in the resulting resin structure will be in physical contact with one another and, hence, free to abrade upon one another. Such physical contact coupled with abrasion may reduce the life of the resulting resin structure, especially when impacted by external forces. Moreover, cutting the resin structure into pellets would simply expose the fiberglass core, so the impact strength of the pellets would be further minimized, if not entirely negated.
Various processes exist for resin reinforcement with fibers, and various processes have been suggested for achieving a thorough impregnation of fibers with molten resin. For example, in U.S. Pat. No. 4,728,387, Hilakos suggests loosening a roving of fibers by passing the roving through tension bars or rolls before or during wetting of the fibers with molten resin. Also, it has been suggested that a roving of fibers may be loosened by passing the fibers through a series of baffles or deflection units, as described by Amaike et al. in U.S. Pat. No. 5,658,513 and by Augustin et al. in U.S. Pat. No. 5,277,566. Glemet et al. provides a similar teaching in U.S. Pat. No. 4,957,422 and U.S. Pat. No. 4,937,028. All four of these patents are incorporated herein by reference.
Notwithstanding the multitude of resin impregnation schemes proposed in the art, achieving a homogeneous distribution of molten resin between and around individual fibers in a roving, as well as removing air trapped between the individual fibers, persist as problems faced by the skilled artisan in achieving reinforced resins with the most desirable physical properties.
SUMMARY OF THE INVENTION
One aspect of the present invention relates to a die for reinforcing a resin with fibers. The die includes a first mold and a second mold positioned with respect to the first mold to define a passageway having an entrance portion, an exit portion, and a mixing chamber situated between the entrance portion and the exit portion. The first mold has a recess and the second mold has a protrusion that extends into the recess of the first mold to angle a portion of the passageway between the entrance portion and the mixing chamber. This angle is generally greater than about 90 degrees with respect to a direction in which the fibers may be drawn along an axis through the entrance portion.
Another aspect of the present invention relates to a process of reinforcing a resin with fibers using the die described above. According to this process, a roving of fibers is drawn into the die and through the entrance portion of the passageway. The fibers then pass through the angled portion of the passageway, wherein the fibers are forced to bend at an angle generally greater than about 90 degrees with respect to a direction in which the fibers are drawn along an axis through the entrance portion. Bending the fibers in this manner causes the fibers to splay before entering the mixing chamber. As the fibers pass into the mixing chamber, the fibers are impregnated with molten resin. The impregnated fibers are then consolidated in the exit portion and extruded from the die.
Dies and processes according to the present invention are advantageous in that they are capable of converting a relatively inexpensive resin having minimal impact strength to a reinforced resin having impact strength rivaling resins which are typically much more expensive in the raw state. The reinforced resin produced according to the present invention is markedly more impact-resistant than other reinforced resins. This is due primarily to the splaying as described above, in that fibers within the reinforced resin are spread out and in a substantially parallel arrangement with respect to one another, as opposed to a random orientation.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention.
REFERENCES:
patent: 3993726 (1976-11-01), Moyer
patent: 4041197 (1977-08-01), Gagné
patent: 4121901 (1978-10-01), Bourrain et al.
patent: 4242380 (1980-12-01), Courtoy
patent: 4312917 (1982-01-01), Hawley
patent: 4588538 (1986-05-01), Chung et al.
patent: 4598012 (1986-07-01), Miller et al.
patent: 4680224 (1987-07-01), O'Connor
patent: 4728387 (1988-03-01), Hilakos
patent: 4783349 (1988-11-01), Cogswell et al.
patent: 4900499 (1990-02-01), Mills
patent: 4937028 (1990-06-01), Glemet et al.
patent: 4957422 (1990-09-01), Glement et al.
patent: 4988278 (1991-01-01), Mills
patent: 4990545 (1991-02-01), Hourai et al.
patent: 5068061 (1991-11-01), Knobel et al.
patent: 5133282 (1992-07-01), Bates et al.
patent: 5205898 (1993-04-01), Wilson et al.
patent: 5213889 (1993-05-01), Cogswell et al.
patent: 5234994 (1993-08-01), Shiraki et al.
patent: 5268050 (1993-12-01), Azari
patent: 5277566 (1994-01-01), Augustin et al.
patent: 5298318 (1994-03-01), Soules et al.
patent: 5325457 (1994-06-01), Bottoms, Jr. et al.
patent: 5409763 (1995-04-01), Serizawa et al.
patent: 5433419 (1995-07-01), Murakami
patent: 5482667 (1996-01-01), Dunton et al.
patent: 5520867 (1996-05-01), Shirai et al.
patent: 5529652 (1996-06-01), Asai et al.
patent: 5540797 (1996-07-01), Wilson
patent: 5582905 (1996-12-01), Beck et al.
patent: 5618367 (1997-04-01), Wilkinson et al.
patent: 5637329 (1997-06-01), Abrams et al.
patent: 5658513 (1997-08-01), Amaike et al.
patent: 5660903 (1997-08-01), Andersen et al.
patent: 5679424 (1997-10-01), Skaletz et al.
Kasha Industries, Inc.
Ratner & Prestia
Weisberger Richard
LandOfFree
Die and process of reinforcing a resin with fibers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Die and process of reinforcing a resin with fibers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Die and process of reinforcing a resin with fibers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2459951