Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
In recent years the need for structural plastic parts has
increased rapidly. Thus directionally reinforced resin sheets which
can be molded into~structural automotive parts such as transmission
supports, door beams and the like have been produced. These directionally
reinforced sheets contain glass strands which have been helically wound
on a mandrel in a crisscross pattern and in amounts ranging between
60 to 80 percent by weight glass. While moldable glass reinforced sheets
of a high glass content produce parts having excellent structural strength
; 10 when molded, it is often desired to provide better modulus characteristics
than are normally realized. Carbon fibers in molded parts are known to
impart good modulus characteristics to resin parts in wbich they are
employed. Blends oE glass and carbon fibers in resins have thus been used
to utllize the qualitles oE strength and modulus that each provides to a
resin matrix~ In attempting to wind carbon fibers with glass fibers in the
preparation of resin reinforced sheeting, considerable difficulty has been
encountered processing the carbon strands. Thus, frequently the carbon
fibers which- are in strand form break in the resin bath or the die. This
appears to be caused by the viscous drag on the strand going through the
bath which causeF the strand of carbon to fllamentize, i.e., separate into
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the filaments forming it, and ultimately break out. In accordance with the
instant invention, a methad has been developecl to wet ttle carbon st~and
with resin and combine it with the glass str~nds to provide a useul
composite strand for forming resin sheet reinEorced with both carbon and
- glass strand.
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The Present Invention
In accordance with a process of the instant invention, novel
carbon and glass strands are wound on a mandrel to prepare resin sheets.
In the sheet preparation process the glass strands are fed from a glass
supply into a resin bath where they are thoroughly wetted. The strands of
glass are then passed through a die metering means which regulates the
quantity of resin which is to be included with the glass strands. The
carbon strand o the composite to be made is fed directly to Lhe back ot
the die used to control the resin content of the glass strand and is
contacted with the resin at the point where the resin backwashes from the
die. Feeding the carbon strand at this point in the process eliminates the
fiberizing of that strand, provides good wet out to the strand and permits
it to be wound on the mandrel with the glass without the attendant breaks
encountered when the carbon strand is fed through a resin bath. The
composite strand of the invention is formed of resin, a plurality of glass
strands and at least one carbon strand.
Detailed Description of the Invention
In the preparation of glass-carbon resin reinforced sheet having
structural characteristics and containing 55 to ~0 percent glass and
carbon with 20 to 45 percent resin by weight, the strands of carbon
~lZ~37~0
and glass are first coated w;th a resin and then are wound on a rocating
mandrel. In the discussion of the process, reference ~ill be ~lade to
the accompanying drawing in which:
~ IGURE 1 is a flow sheet in perspective of the equipment used to
manufacture the resin-glass-carbon sheets of the instant invention;
FIGURE 2 is an enlarged view in perspective of the resin applica-
tion section of the process depicted in FIGURE l; and
FIGURE 3 is a section view looking into the resin application
pan 9 to show the die 13 and point of entry of the carbon strand.
In the preparation of the resin-glass-carbon composites of
the instant invention a plurality o glass strands are used. ~s shown
in FIGURE I for illustrative purposes, only six glass fiber forming
packages Z are employed. These packages 2 are mounted on a stand or
cree~, not shown, and the glass strand ends I from each of the packages
are threaded through eyelets 4 and 5 mounted on the wall member 3, typically
a sheet metal plate. In the illustration of FIGURE I the upper row of
glass forming packages have their strands ends 1 passed through eyelet 5
and the lower row strands ends l are passed through eyelet 4. The physically
combined strands form two glass ribbons 1' which are passed under the
retaining bars ll and 15 of the resin tank 9. These strands 1' and 1 are
then fed through the dies 12 and 13 and located at the forward end of the
pan 9. Mounted on the top of the wall 3 are two packages 18 and 18' which
contain carbon strands 8 and 8', respectively. The carbon strands 8' and 8
are introduced into the dies 12 and 13, respectively~ by passing them
through the resin backwash 14 a~cumulating as the dies wipe resin from the
surface of the glass strands l' and 1. The consolidated glass-carbon
strands 19 and 19', which e~it the dies 13 and 12, are then consolidated
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into a band 17 in guide eyelet 22 located on a traveling guide 21 an~ this
ribbon is wound on a rotating mandrel 15 to the desired thickness. ~Eter
the composite reaches its desired thickness, the mandrel 15 is stopped and
the resulting sheet is cut from its surface and the process i9 repeated.
The p~ocess generalLy depicted in the drawing is obviously
subject to many variables. Thus, while only a one strand ribbon 17 is
shown in the drawing as being wound on the mandrel 15, this is solely
for illustrative purposes. The mandrel may have a band or ribbon of many
- collimated parallel composite strands wound at the same time on its surface.
Similarly the number of glass ends used to form the strands at 1' can
be varied. Thus one end can be used as the strand 1' or any multiple
of ends can be used to`form the strand l'. Typically the number of ends
employed to form the strands 1' has ranged from 1 to 10 or more. The
width of the band 17 desired in the final produce determines the number
and diameter of strands,that will be used to Eorm the band. By width
of band is meant the width measured perpendicular to the band direction.
In the process shown in the drawing the mandrel l5 is rotating
in a clockwise direction on a shaft, not shown, which is driven by a
suitable motor. The guide plate 21 reciprocates in a horizontal plane
and lays the composite strand 17 do~ on the surface of the mandrel 15.
The sCrand 17 is normally laid on the mandrel 15 at a predetermined
helix angle to provide directional reinforcement properties to the finished
sheet. The helix angle is the included acute angle created by the inter-
section of the band 17 on the body of the mandrel 15 with a line on the
body of the mandrel parallel to the longitudinal axis of the mandrel. This
angle for the structural sheets produced by this process is generally in
the range of 60 to ~9 degrees. The wind angle of the mandrel in relation
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to the strand 17 is the included acute angle created by the intersectio~ o
the band 17 on the body of the mandrel 15 with a Line on the body of the
mandrel perpendicular to the longitudinal axis of the mandrel. In a
-~ typical use of the process this angle is between 30 to I degrees.
- In the normal operation the mandrel 15 rotates continuously
during the process and the guide 21 reciprocates in a horizontal plane
causing the ribbon or band 17 co be laid down on the mandrel 15 in a
crisscross fashion to form layers of composite on the surface of the
mandrel. For purposes of this disclosure a layer is Eormed when the
band 17 has covered the mandrel in both traversing directions. The finished
sheet containing the glass and carbond serands will contain the number of
layers desired to produce a produce of the desired density in pounds per
square foot.
The resin pan g during the operation is constantly supplied
with resin 10 to insure that sufficient resin is maintained in the pan 9 to
thoroughly wet the glass strands 1 and 1' whic~ are passed through it under
the bars 11 and 15. This can be done continuously by providing an automatic
feed inlet and overflow system or the resin can be added manually as
required. The pan Y, depending on the width of the mandrel 15 can remain
stationary or it can be reciprocated in a horizontal plane coordinated with
the movement of the plate 21.
The strand and article of the invention may be formed using
any suitable resin. Typical of suitable thermoplastic resins are thermo-
plastic resins such as polyethylene, polypropylene and polystyrenes.
- The thermosetting resin employed in the syscem may include many types and
typically resins such as vinyl esters, quick curing epoxy resins and
general~purposes polyester resins have been employed. Isophthalic polyester
74~
resins have been found to be particularly eEEective in making the compos ites
of this invention and are preferred. Resins s~lch as B-sta~e c~lring epoxy
resins and thickened polyesters are desirable as they may be stored after
remova} from the mandrel and then cut and molded to cure at a later date.
- Typically polyesters which may be employed in the invention are the class of
resins shown and described in U.S. Patent No. 3,840,618.
An important consideracion in preparing composites is the
regulation of the resin content of the Einal product. In this process
this is accomplished by regulating the size of the orifice in the dies
12 and 13. In general i~ has been found desirable to maintain these
orifices in the range of 0.014 to 0.078 inch.
The graphite strands fed to the system may be pulled directly
from the wall member 3 as shown or can be drawn from a creel placed closer
to the front end of the pan 9. The point of entry of the carbon strand
in the resin pan is an important consideration in achieving success in
forming the composite ribbons or bands 19 and 19' however. The residence
time and drag on the carbon strand must be minimized to prevent damage or
degradation to the strand. Thus, it is important that the carbon strand
be introduced into the process at or close to the entrance to the dies and
preferably in the central area of the resin backwash of that die. This
prevents the carbon strand from receiving any excussive strain of being
pulled through the resin and allows the strand of carbon to enter the
system with little or no viscous drag applied to it.
The sheet composites and composite strands produced by this
process on a volume basis generally contain 50 to 5 percent carbon strand
and 5 to 50 percent glass strand. ~owever, it is within the invention
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to have on a volume basis between about 20 percent and 95 percent glass
and between about 80 percent carbon and about 5 percent carbon st~nd.
This corresponds to between about 35 and about 98 percent by weight glas~s
strand and about 65 percent to 2 percent by weigh~ carbon. The strands of
carbon and glass are fed to the system and the composite strand wound on
the mandrel at speeds ranging between 50 and 500 Eeet per minute.
The resins used are supplied to the composite strands and
typically the sheets formed are placed between two layers of clear sheet
such as polyethylene. Thus in practice the surface of the mandrel is
covered with a polyethylene sheet prior to winding the resin containing
composite strand. ~hen the requsite number of layers have been applied to
the mandrel, the mandrel is stopped and the composite sheet is covered with
another layer of polyethylene sheet and then cut Erom the mandrel. By
sandwiching the composite sheet between the polyethylene layers, the resin
composite can be readily handled and stored until a molded part is to be
made from it. Heat applied to the composite sheet during molding converts
the sheet product into a thermoset, hardened part.
Carbon strands are produced by treating organic fibers by
pyrolysis to produce strands of carbon Eibers. Thus, carbon filaments
have been produced by pyrolyzing rayon precursor yarns, polyacrylonitriles
and the like. Several of these strands are available in industry today
and have been described in the literature. (Modern Plastics Encyclopedia,
54, lOA, page 172, Oct-. 1977; Advanced Materials, C.Z. Carroll-Porczynski,
Chemical Publishing Co., N.Y. 1962; Industrial Chemistry, 7th Ed., pg. 342,
Van Nostrand Reinhold Co., N.Y., 1974.) A particularly useful ~strand
for use in the instant process is a carbon fiber called CELION~ manufactured
by Celanese Corporation.
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~Z~40
In a typical application of the presellt process a resin-glass-
carbon sheet was made by Eilling the resin pan with a resin mix~ure
containing 90 parts of an isophthalic polye.ster resin, 10 parts o ~tyrene
monomer, 0.5 part o zinc stearate, 1 par~ ~ertiary butylperbenzoate ancl
3.5 parts of magnesium oxide thickener.
Twelve glass Eiber forming packages were mounted on a creel,
each of the packages containing K-37 glass strands. These strands have 400
glass filaments, each filament having a diameter of 0.0005 inch. Three
glass ribbons were prepared by pulling strands from four packages and
combining them prior to introducing them into the resin pan. A total
of three glass ribbons were passed through the resin pan continuously at
a rate of 100-200 feet per minute. The resin pan containing the resin mixture
referred to above w~s maintained constantly supplied with res;n during the
run. The three gldss strands passing through the resin pan were withdrawn
through three precisiQn dies, each having a diameter of 0.045 inch. Three
carbon strands were fed into the system by passing one of each into a
die through which each of the three glass ribbons was being féd and on
the resin pan side of the die so that the carbon strand entered the die
near the center portion in the backwash of resin that was generated by the
die in wiping exce~ss resin from the surface of th`e glass ribbon being ~ed
thereto. In passing through the die, the carbon strand becomes wetted with
the resin contained in the die and the backwash and is physically combined
with the glass ribbon passing through the die to thereby form three con-
solidated glass-carbon bands or ribbons. These three consolidated ribbons
were passed through three guide eyes positioned on a reciprocating guide
de~ice positioned above a rotating mandrel. 1'he strands were wound on the
surface of the mandrel in side by side relationship at a helix angle o
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85.4 degrees and a wind angle of 4.6 degrees. Ttle reciprocating guide was
passed back and forth above the surface oE hte mandrel and the consolidated
strands were wound until three layers were la,i~l on the mandrel, surEace.
The mandrel was then stopped and the composite strand-resin sheet was
removed. The Einished sheet was cut to a blank si%e for molding flat
panels. Panels were molded from these blanks on a press and formed satis-
factory structural panels.
While the invention has been described with winding of the
strands onto a mandrel it is also possible to use the composite strand
of resin, carbon and glass in other ways. ~le strand would be wound onto
spools for later use. The spools could be unwound for use in winding at
remo~e locations. The spools also could be used irl weaving woven rein-
forcement or used in only certain portions of articles where extra rein-
forcement was desirable. The strands could also be wound together to form
cables. Further the strands could be fed directly from the bath onto a
belt in swirls and then into a laminator.
While the invention has been described with reference to
certain specific embodiments, it is not intended to be limited thereby
except insofar as appears in the accompanying claims.
