Note: Descriptions are shown in the official language in which they were submitted.
lO9S786
METHOD FOR RRODUCTION OF FIBER R$INFORCED RESIN STRUCTURES
Background of t`he Ihvention
The present invention is directed to improvements in
a process for the production of fiber reinforced resin
structures, known as pultrusion.
Pultrusion is a technique in which resin-coated fibers
are pulled through an elongated heated tube which induces
shape to the structure and cross-linkings of the resin.
Typically, the fiberous material is fed through a liquid
resin bath where individual fibers are thoroughly coated
with the resin. Excess material is stripped from the
reinforcement by brushes or rollers. The saturated
resin reinforced fibers enter an elongated heated die
and post curing in an oven immediately following the
die have been employed. In the process, the elongated
die is relied on as the primary source of heat to effect
cure and provides heat to the resin by conduction.
Pultrusion and its general applications are described
in "Plastics Design and Processing", May 1976 (pp. 8 and 9),
and in U.S. Patent 2,871,911 to Goldsworthy et al.
A modification of the pr~cess is described in U.S. Patent
2,948,649 to Pancherz.
Essential to the production of high strength fiber
reinforced resin structures is a condition that all the
fiberous elements be completely wetted by the resin,
that the fiberous elements do not break, and that an
absolute minimum of binding resin remain in the
finished structure to minimize the distance between
10~578~
adjacent fibers. The pultrusion process, as it has been
practiced, has not been found to fully achieve these ends
and has been overly costly in the energy required to achieve
drawing of a fiber reinforced resin structure into a desired
configuration. In addition, the use of elongated dies can
result in a disfigurement of the surface of the article due
to localized accumulation of cured resin within the interior
of the die.
Summary of the Invention
In accordance with the present invention there is
provided a process for the production of fiber reinforced resin
structures which comprises, under tension:
(a) coating a plurality of continuous fibers in spaced
relation to each other with a liquid heat curable thermosetting
resin composition at a resin temperature below the temperature
at which cure of the thermosetting resin is initiated;
~ b) converging the coated fibers to a common point
to achieve contiguous contact of fibers while removing excess
of the liquid heat curable thermosetting resin from the fibers;
(c) spreading the resin coated fibers from the common
point to achieve spaced relation between the resin coated fibers;
(d) passing the resin coated fibers in spaced relation
to each other through at least one elongated radiant preheating
zone having at least one heated internal surface, the internal
surfaces of the preheating zone being in spaced relation to the
spaced resin coated fibers, said preheating zone raising the
applied resin by radiation and convection to a temperature suf-
ficient to reduce the viscosity of the resin relative to the
introduction viscosity of the resin to the radiant pre-heating
zone and initiate cure of the resin;
~957~6
(e) converging and passing the heated resin coated
fibers through a structure shaping orifice of at least one
first cold shaping die position between said radiant preheating
zone and a next radiant heating zone, said cold shaping die
being at a die temperature substantially below the temperature
at which curing of the resin is initiated;
(f) passing the resin coated fibers from the first
cold shaping die through a plurality of elongated radiant heating
zones, each having at least one heated internal surface, each
heating zone being spaced from each other and from at least one
interposed cold shaping die which is relatively narrow with
respect to the length of a radiant heat zone and having a structure
shaping orifice, the internal surfaces of each heating zone being
in spaced relation to the resin coated fibers, said radiant heating
zones raising the applied resin by radiation and convection to a
temperature above the temperature of the radiant preheating zone
and sufficient to reduce the viscosity of the resin relative to
the introduction viscosity of the resin to a radiant heating zone
and initiate further cure of the resin;
(g) drawing the fibers and resin through the orifices
of ~ach cold shaping die between each radiant heating zone at a
die temperature substantially below the temperature at which curing
of the resin is initiated;
(h) drawing the resin coated fibers through at least
one final cold shaping die following the last of said radiant
heating zones, said die being at a temperature substantially below
the temperature at which cure of the resin is initiated, the resin
being at the gel point at or prior to contact with said final die.
Also in accordance with the invention there is provided
a process for the production of fiber reinforced resin structures
which comprises, under tension:
(a) coating a plurality of continuous fibers in spaced
relation to each other with a liquid heat curable thermosetting
3 -
:1~9S'786
resin composition at a resin temperature below the temperature
at which cure of the thermosetting resin is initiated;
(b) converging the coated fibers to a common point
to achieve contiguous contact of fibers while removing excess
of the liquid heat curable thermosetting resin from the fibersi
(c~ spreading the resin coated fibers from the common
point to achieve spaced relation between the resin coated fibers;
(d) passing the resin coated fibers in spaced rela-
tion to each other through at least one elongated radiant pre-
heating zone, having at least one heated internal surface, the
internal surfaces of the preheating zone being in spaced relation
to the spaced resin coated fibers, said heating zone raising the
applied resin by radiation and convection to a temperature suf-
ficient to reduce the viscosity of the resin relative to the
introduction viscosity of the resin to the radiant preheating zone
and initiate cure of the resin;
(e) combining an inner continuous elongate structure
with the heated resin coated fibers in a predetermined position
of the elongate structure relative to the resin coated fibers and
converging the resin coated fibers about the elongate structure;
(f) passing the heated resin coated fibers and added
elongate structure through a structure shaping orifice of at
least one first cold shaping die position between said radiant
prehea~ing æone and a next radiant heating æone, said cold shaping
die being at a die temperature substantially below the temperature
at which curing of the resin is initiated;
(g) passing the resin coated fibers and added elongate
structure from the first cold shaping die through a plurality of
elongated radiant heating zones, each having at least one heated
internal surface, each heating zone being spaced from each other
and from at least one interposed cold shaping die between each
heating zone which is relatively narrow with respect to the
- 4 -
'~ i
1(~95786
length of a radiant heat zone and having a structure shaping
orifice, the internal surfaces of each heating zone being in
spaced relation to the resin coated fibers, said radiant heating
zones raising the applied resin by radiation and convection to a
temperature above the temperature of the radiant preheating
zone and sufficient to reduce the viscosity of the resin relative
to the introduction viscosity of the resin to the radiant heating
zone and initiate further cure of the resin;
(h) drawing the fibers, resin and added elongate
structure through the orifices of each cold shaping die between
each heating zone at a die temperature substantially below the
temperature at which curing of the resin is initiated; and,
(i) drawingthe resin coated fibers and added elongate
structure through at least one final cold shaping die following
the last of said heating æones, said die being at a temperature
substantially below the temperature at which cure of the resin
is initiated, the resin being at the gel point at or prior to
contact with said final die.
The process of the present invention comprises, under
tension, first coating a plurality of continuous fibers spaced
in relation to each other with a molten, heat curable thermosetting
resin composition, the resin being sufficiently liquid to at least
partially coat the fibers but maintained at a temperature below
that at which cure of the resin will be initiated. The coated
fibers are combined in contiguous relation and passed through an
excess resin removal zone then spread apart and passed through a
preheating zone in spaced relation. There the spaced fibers are
heated by at least one radiant heating surface spaced from the
fibers to achieve a reduction of resin viscosity then combined and
passed through a first shaping die. Any fiber or fibers to be clad
by the resin coated fibers is added ahead of or at the first
shaping die. The
.. jj. " . ... .
~'
95786
1 ~precoated recombined fibers are then passed through a
¦plurality of elongated radiant heating zones in series,
¦each providing at least one heated surface, the surfaces
¦of the heating 20nes being spaced from theresin impregnated
5 ¦fibers, the radiant heating zones of the series being
¦separated from each other by at least one cold shaping
¦die, each die being narrow relative to the length of the
¦radiant heating zones. In each radiant heating zone, the
¦resin is heated, by radiation and convection, to a
10 ¦temperature sufficient to induce some polymerization and
¦still reduce the viscosity of the resin, preferably, to
¦belsw its initially applied viscosity. This makes the
resin more mobile to increase wetting of the fiber surfaces
l as an aid in shaping to the final structure. Resin
1~ temperature achieved in each heating zone is surficient to
induce partial cure of the resin which induces a viscosity
sufficient to prevent the resin from draining from the
fiber surfaces.
As indicated, between each radiant heating zone, the
~0 fiber and coating resin are drawn through one or more
relatively narrow cold shaping dies. The shaping dies are
maintained at a temperature substantially ~elow the temper
ature at which curing of the resin is initiated. In passing
through the orifice of each die, the resin and fibers are
25 progressively formea into the desired cross-sectional
configuration ~7ith attendant expulsion of excess resin.
This maximizes radial compression of the fibers in respect
to each other. The dies should be maintained at a
temperature sufficiently low suc~ that cure of the
3 expelled resin within the die or on the die surface will
s~ .
. ~ ' .
95786
1 not be promoted. This permits expelled resin to flow over
the die surface. If the resin which is expelled tends to
collect on the surface of the die, it can be removed by
raising die temperature and/or by an air blast or the
like.
Gel point, the point at which viscosity can no longer
be reduced by application of heat and where cure w ll be
accelerated with a large release of heat per unit mass, is
delayed until at or just before the last die. At this
point, the resin is in a ~irm gel state where the structure
retains its configuration but remains workable to a degree
to enable any excess resin to flow and be removed from the
surface by a ~inal shaping die. Finzl cure is reser~ed,
if it is used, to a curing zone following the last die.
Following each die of the seriesl except for the last,
the resin is heated to achieve a reduction in viscosity
and to further promote cure towards the gel point with an
attendant increase in viscosity after passing through a
~iscosity minimum during passage through each heat zone.
20 In passing through the final heat zone of the series, the
resin-coated fiber may reach the gel point.
8eyond the final die, there may be and preferably is
positioned a radiant heated curing zone where, through the
application of heat, cure from the gel point to the f ixed
25 resin state is achieved such that the applied resin will
become totally cured and set to enable collection of the
structure as a product. Elimination of the radiant heating
curing zone only extends the distance of travel of the
product to a windup roll so that cure will be complete
3~ before the Wil~Up roll is reached.
~ , A~ .
1095786
1 In the practice of this invention, each die is to be
maintained at as low a temperature as conveniently possible
to act as a shaping die while tending to retard cure during
the shaping process. The die may be partially heated by
provided heating means or allowed to be heated simply to
what~ver temperature is induced in the passage of heated
parallel fiber-resin matrix therethrough and heat of
radiation and/or convection from the adjacent heating zones.
It is essential that the die surface be maintained at a
temperature sufficiently high such that the resin which
exudes from the fiber-resin matrix passing through the die
onto the surface of the die will flow from and be removed
from the surface before thickening or cure occurs, This
prevents the formation of cured resin at the die orifice
which would otherwise increase friction, disfigure the
surface of the article being shaped and, perhaps, induce
rupture of the fibers passing through the die.
Rate of passage through the dies and heating zones
is normally controlled by the number of heating zones and
~0 dies in series, the minimum number of heating zones and
dies respectively employed being two. As the number of
heating zones and dies are increased, the rate of feed
through the system can be increased materially with the
. proviso that attainment of the gel point is precluded
-2~ until contact with or just prior to contact with the final
die. In general, the point relative to the final die at
which the resin reaches the gel point becomes less critical
as the number of dies increase.
~ _p
I ll~9S7f~6
1¦ By passing the coated fibers after contact in
spaced relation to each other through;thepreheating zone,
there is achieved a more uni~orm coating of the fibers
l which in end minimizes the amount of resin required to
51 achieve a uniform hlgh strength product.
¦Description of the Drawings
I _
FIG. l is a schematic illustration of apparatus
lused and the steps which occur in practice of the process
10 ¦of this invention;
¦ FIG. 2 illustrates the relative viscosity of the
¦applied resin at each stase along the process; and
¦ FIG. 3 illustrates the presently prepared steps of
¦processing the fibers to the first shaping die.
15 I
Detailed Description of the I~vention
I .
¦ With reference to FIGS.l and 3, the fibers to be
¦formed into a fiber reinforced resin structure or for
¦embracing another fiber in strengthening or protective
20 ¦(ruggedizing) relationship are provided by plurality of
¦creels or spools 10 and are drawn under tension provided
¦~by take-up reel 12 and passed, if desiredl through comb
¦11 to remove splinters and the like. They may as shown in
¦FIG. 1 be passed over roller 14 and under 16 of resin
~5 bath 20 ~o achieve an initial resin coat. In this instance,
the coated fibers may be passed over roller 18 which acts
as squeegee to remove excess resin. Other means of
removing excess resin may also be used. The presently
preferred route is detailed in FIG. 3.
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1(~95786
With reference to FIG. 3, the fibers ~rom comb 11 are
passed over tensioning rolls 15 and spread in a fan-like
array by orifices 17 in the inlet end wall of resin bath
20. The orifices are fitted with seals to prevent resin
leakage. The fibers are coated with resin in spaced
relation to one another and combined at sizing orifice 19,
also provided with a seal to prevent leakage, then spread
apart by spacing dies 21 and maintained in spaced relation
through preheating chamber 22. Orifice 19, in addition to
bringing the fibers into contiguous contact, acts as a
means to remove excess coated resin serving for this
purpose the equivalent of squeegee roll 18 of FIG. 1.
The resin supplied is a heat curable thermosetting
resin composition maintained in a liquid state at ambient
or elevated temperatures.
The nature of the thermosetting resin may be varied
widely and include, among others, epoxy resins, such as
epo~idized cyclopentadiene; polyesters, phenolformaldehyde
resins; ureaformaldehyde resins; diallyl phthalate resins;
silicone resins, phenol-furfural resins; urethane resins
and the like~depending upon the desired composition of
the finished product. Included in the melt is a high
temperature initiator or hardener which is latent in
respect to initiation of cure while in the molten bath
but at some elevated temperature will initiate and
propagate cure of the resin to a thermoset end product.
Typical of such hardeners are aromatic amines. Included
as desired are accelerators, diluent resins, fillers,
colorents, flame retardants, and the like. The temperature
of bath 20 is not narrowly critical so long as it is
-- 10 --
l 1~95786
1 maintained at a temperature below tho temperature at Wl)iC]l
cure of the resin will be initiatcd. This is ~:no:~n a5 '.he
resin H~-- stage. Generally, a ty~ical J~at!l tcmperature will
ranse from about 20 to abou~ 30~C. ~gitation and
S pressure-vacuum recyclin~ of the bath may be used to
occlude the presence of air bubbles or the like as is
r-quired,
As fibers are drawn through the bath and over roller 18
or through orifice 19, they are precoated with the thermo-
setting resin melt and carried to and passed under tensionthrough a first radiant heating chamber 22 in spaced relation
to each other, Orifice 19 serves in the preferred embodiment
to combine the fibers just ahead of chamber 22 while the first
spacing die 21 spreads them apart for passage through preheat
chamber 20. This has been found to provide a more uniform
coating on the fibers and in the end results in a prod,uct of
more uniform axial strength with a minimum of resin necessary
to achieve the desired strength. With reference to FIG. 2,
in radiant heating chamber 22, which servès as a preheat
, 20 chamber, the resin is heated from radiant energy received
from a heated surface(s) always in spaced relation to the
surface of the resin coated fibers which are spaced from
each other and by convection to initiate polymerization and
break resin viscosity. This induces an initial reduction in
~iscosity (a-b? such that the resin will become more fluid
and more thoroughly and uniformly wet the fibers. Cure
initiates with an attendant increase in viscosity (b-c) to
return to about the initial viscosity. This is to prevent
the resin from draining from thé fiber surfaces before or
at shaping die 24. Typical internal preheat zone temperatures
~QgS786
1 are from about 85 to about 130C, depending on the initiation
temperature required b~ the accelerator to start cure. The
cure initiates and begins the "B" stage at about the minimum
point (b) of the viscosity curve illustrated in FIG. 2.
With initiation of cure, viscosity increases as some of the
cross-linking reactions occur.
The resin and fibers are then brought into contact
with and passes through the orifice a first cold shaping die
24 where an initial shape is provided to the fiber reinforced
resin matrix with exclusion of a portion of the resin.~ The
resin is forced from the matrix as it passes through the
die and normally runs over the die surface. To facilitate `
its expulsion from the die orifice, a blast of a fluid,
such as air, may be induced from jet 29. This prevents the
resin from curins or congealing on the surface of the die.
Ahead of the first cold shaping die, there may be
positioned one or more guide grids 25 used to position the
fibers in proper spacial relation to one another for entry
to die 24 and for addins, if desired, a fiber from reel 27
to be surrounded by the other fibers. The fibers passing
through the preheating zone are as shown in FIG. 3 in a
spaced parallel or converging fan-like configuration and
formed into a circular pattern by grid 25 with a central
opening for introduction of a fiber from reel 27 for passage,
in combination, through a circular shaped die orifice.
Little, if any, resin is lost in passing the resin coated
fibers through grid 25.
i~ . . ~ ' , ' '
5786
1 By "cold shaping" or "relatively cold shaping" die 24,
there is meant a die which is relatively narrow in respect
to the length of the radiant heating zones and maintained
at a temperature below the temperature of adjacent heating
zones and ~elow the temperature at which cure of the resin
will be promoted and which serves to suppress the curing
process to the extent the expelled resin will flow over the
die surface and away from the die orifices. To this end,
the die may be allowed to achieve whatever surface temperature
1~ results as an incidence to the passage of the heated fibers
and resin through the die, and from radiation and convection
- from adjacent radiant heatlng zones to promote flow of
expelled resin over its surface. It may, if desired, be
internally heated to promote flow of the expelled resin
over its surface as required to prevent resin from congealing
on the die, particularly at the die orifice. Effective die
; temperatures up to about 70C have been employed.
After passing through cold shaping die 24 where the
resin may have reached a relatively constant viscosity and
20 with reference again to FIG. 2, the composition is passed -
through a second radiant heating ~one 26 having a heated
surface spaced from the resin and fiber where through an
increase in temperature induced by radiation and convection,
the viscosity of the resin is again seduced (d-e) and cure
~5 promoted (e-f). After passing through the minimum (e) as
shown in FIG. 2, viscosity increases.
The sequence is repeated as often as desired and, in
practice, as many as five or more dies in series have been
used until a final cold die 28 treated in the same manner
3~ as die 24 is reached.
~957~36
1 The process is controlled such that the structure
reaches the gel point (g) at or just prior to final
shaping die 28.
The "gel point" is where the resin is in a glassy
solid state, still sufficiently soft to mold and remove
excess resin to thereby enable the formation of the final
shape to the article, but is otherwise beyond the point
where a viscosity reduction with heating will occur. It
is also the point where cure will be irreversibly accelerated.
Such as is shown in FIG. 2, viscosity will on a relative
basis rapidly increase with time with a high exotherm per
unit mass.
Following passage through final cold shaping die 28,
the shaped product is normally passed through a final
15 radiant curing zone 30 where, through the application of
heat by radiation and convection, cure is accelerated and
the resin sufficiently cured to enable the final product
to be drawn by a take-up reel 12.
In the practice of the process, the heating zones
20 following the first cold shaping die are typically maintained
at a higher temperature than the first preheating zone and
in the instance of high temperature cured epoxy resins in
a range of about 170 to about 220C or at least at a
¦temperature sufficient for the resin to break its viscosity
¦to enhance wetting of fibers and filling interstices between
¦the fibers. The post curing zone 30 is maintained at the
same, lower or higher temperature as one of the preceding
zones. The curing zone may be operated in the same
¦temperature range.
30 ¦ Typically, resin content at the exit o~ the first die
¦of the series is normally at a level from about 20 to about
;~ ~
I
1 10~57B~;
1 40% resin based on the weight of resin and fibers and will
be reduced by about 20 to about 25~ by weight of the
original resin content by the time the final die is reached.
The precise amounts will vary depending on the desired
S degree of compaction between fibers.
The heating zones may be of any desired cross-sectional
shape and of a shape independent of the cross section of
the article to be produced. Heating may be by resistance
coils, heating tapes, fluid flow and the like with suitable
thermostatic control. Heating of the resin and fibers is
by radiation and convection. Conduction is not employed
since there is no contact between the resin and fibers
with the internal surfaces of the radiant heating and
curing 20nes.
Each of the radiant heating and curing zones used in
the practice of the process of this invention are in
spaced relation to the resin and fibers which pass through
them. Their function, except for the curing zone, is to
cause viscosity reduction of the resin while polymerization
is stepwise progressed to the gel point, but play no part
in shaping of the final structure. This function is reserved
to the relatively narrow cold shaping dies. While the
~adiant heating zones may range from 2 feet or less to 8
feet or more in length, the shaping dies will have a
thickness of from about 1/64 to 1/4-inch, depending on
the rigidity necessary to accommodate the load imposed by
the passage of resin and fibers through the orifices of the
dies. Orifice openings may be from 0,01 inch or less to 0.5
inch or more. The die orifices are normally pro~ided with
rounded inlet edge surfaces to reduce friction and promote
removal of exuded resin.
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1 ~095'78~i
1¦ As a consequence of employing narrow shaping dies which
cooperate with adjacent radiant heating zones which play no
shaping function, the energy required to achieve a finished
¦ product as compared to the techniques taught, for instance,
5 ¦ in U. S. Patent 2,948,649 is materially reduced. In
addition, the continuous removal of the exuded resin over
¦ the surface of the die ei'her by flow alone and/or with an
¦ air blast, there is avoided buildup of resin at the orifice.
¦ This avoids surface defigurement which can readily occur in
10 ¦ an elongated heating or cooling shaping section as described
¦ in such patent. Surface irregularities within elongated
¦ shape controlling sections, for instance, can entrain resin
¦ which become stagnant and tends to cure leaving rough spot~s)
¦ to increase friction and cause defigurement of the article
15 ¦ to be shaped.
¦ ~he process of this invention may be used with any of
¦ the known fiberous materials including metallic, semi-metallic,
¦ natural organic, synthetic fibers, glass fibers, and combinations
¦ thereof. Illustrative fibers are glass fibers, steel fibers,
~0 ¦ AramidTM fibers, graphite fibers, and the like. Included
¦within the fibers may be fibers which are to be surrounded
¦ by other protective coatings include soft metal fibers, such
¦ as copper, optical fibers, and the like.
. ¦ The process of this invention is applicable to forming
25 ¦ configurations of any desired cross section. They may be
¦ formed as relativel, thin planar structures containing
¦ electrical conductors, optical fibers, fluid conductors, and
the like contained within a-surrounding fiber reinforced
resin structure, the shape of which is determined by the
cold shaping dies. Multiple coatin~ of individual fibers may
also be employed with precoating of fibers acco~plished in
'.~ . ~
109S~786
1 tandem operatiolls or 'wo or morc coating units opcratcd
as desircd to meet the eods of the end prod~lct rcquircd.
For instance, in the situation where a central fiber is
surrounded by stren~thening fibers, the ccntral fiher
may be coated with a release material to ~hich the resin
will not adhere or bond to provide a fiber which, in
substance, is surrounded by a fiber reinforced cured resin
casing which can be stripped from the central fiber
without breaking adhesive bonds between the resin and the
central fiber.
By the practice of the ins~ant inventlon, more precise
control over the shape and guali~y of the end product is
achieved at a material reduction in power consumption.
In addition, fibers can be drawn through the shaping
apparatus without brea~ing and can be compacted to the
maximum extent possible.
While nowise limiting, the follot~ing examplesillustrate
the practice of the process of this invention.
2 Example l
There was maintained a molten heat curable resin
~e ~
bath comprised-of lOO parts by weight ~poxy Resin 826~ -
manufactured and sold by Shell Chemical Company, 26 arts
~ e ~
by weight of an hardener known as Jeffamine 23~ manufactured
2 and sold by Jefferson Chemical Company, and 6 parts by
~ a~
weight of an accelerator, ~ccclerator-~9~ manufactured
and sold by Jefferson Chemical Company. Bath t~mperature
was maintained at 15.6C. To reinforce coat an enameled
9578~i
1 copper ~ire, strands of a glass fibcl- ~n~n as S-901
manufacturcd ~nd sold by Owens Corning Corporation were
drawn through the bath at a rate of 12 feet per minutc.
The resin coated glass fibers ~ere then passed through a
first radiant preheating chamber maintained at 93C to achieve a
first viscosity reduction of the resin. The length
of the preheating chamber was 8 feet. The wire was -
centrally introduced to the glass fiber-resin matrix
and with the surrounding glass fibers and resin was dra~m
0 through a first die at a temperature of 65C,
ana then through a second radiant heating zone of
6 feet in length maintained at 175C to achieve a second
viscosity reduction in the binding resin. The heated
preformed cable was then dra~n through a second die again
15 at a temperature of 65C as induced by the drawn matri~. -
The resin had reached the gel point at the second die.
After passage through the second cold shaping die, the
gelled resin impregnated glass fiber reinforced ~7ire ~Jas
passed through a post curing chamber maintained at 175C.
2~ Chamber length was lZ feet. Following cure, the product
was wound onto a reel.
. '. -' . ' ..
Example 2
There was coated,using the resin system of Example 1,
~ ends of Owens Corr.ing S-901, each cont~ining about
201 glass filaments and passed through the resin bath
at the rate of 12 feet ~cr minute. Aftcr the initial
coating, the resin and fibers are passed over a squeegee roll
.~
~9S7~
to the extent o~ providing ~ibexs containing ~rom about
25 to 30% by wei~ht resin based on the weight of resin and
fibers. The resin impregnated fibers were then passed through
a first radiant preheating zone maintained at a temperature of
about 110C. The preheating zone as all subsequent heating
zones, was constructed o~ a "U" shaped channel 4" wide across
the base and having 2" high sides. Heat was provided by thermo-
statically controlled heating tapes along the length of the
channel and covered by an aluminum plate. The zone is closed
at the top by a removable aluminum lid. The radiant preheating
zone was 8 feet long.
After emerging the preheating zone, an optical fiber of
5.0 mil diameter buffered to a thickness of 20 mils with a room
temperature cured silicone rubber by the method as described in
my West German Application Serial No. P 26 28 393.2 laid open
to inspection on 17th February 1977, was added using two guide
grids in series. The guide grids centered the buffered optical
fiber which became surrounded by the resin coated fibers. The
combination was drawn through a first cold shaping die having
an orifice of 0.048 inch in diameter and the first of five
additional radiant heating zone having the same construction as
the preheating zone, but of length of about 30 inches. The cold
shaping die after the first of the radiant heating zones has an
orifice of 0.044 inch in diameter and the orifice openings of
the remaining dies was 0.04 inch. Spacing between heating zones
was about 6" between which the die was positioned. Radiation
and convection adjacent heating zones maintain die surfaces at
about 66C.
-- 19 --
S~786
1 In~ernal heating zone tcmperaturc of each o~ the five
radiant heatin~ zones t~as about 171C. The resin
reached a gel point just prior to the last die. In
the process, about 20~- by weight of the resin is removed
from the structure leaving a final structure containing
from about 22 to about 25~ by weight resin based on the
~eight of resin and fibers. The structure was passed to
a curing zone of the sectional configuration and structure
as described ab~ve and maintained at 177C. The length
of the curing zone was 28 feet. Using the operation
glass fiber ruggedized buffer optical fibers up to 10,000 --
feet in length were produced.
., - - ~
Ex'ample' 3
The procedure of Example 2 was repeated to produce
structures of 0~5 inch in outside diameter. Solid
structures as well as containing embedded metal and
buffered optical fibers were produced. For a structure
of 0.5 inch outside diameter,feed rate was reduced to
6 feet per minute, the radiant preheating zone was
maintained at about llO~C, the intermediate radiant
heating zones at 204~C and the curing ~one at 177~C.
As will be appreciated by those s~illed in the art,
any functional die between radiant hea~ing zones may consist
of a plurality of dies in series, and any radiant heating
zone between two dies may consist of a plurality of radiant
heating zones in series. '
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1~95~86
1 Example 4
There was maintained, at a temperature of 21 to
24C, a molten bath of a heat curable epoxy resin formulation
comprised of 100 par~s b wei ht Epoxy Resin 826, 32
l~
B parts by weight of T~nox~Hardener manufactured and sold
by Naugasett Chemical Company, and 4 parts by weight of
D.M.P. No. 30 Accelerator manufactured and sold by Rohm
and Haas Chemical Company. To reinforce (ruggedize)
a buffered, graded`index, optical fiber of Type SCVD
supplled by International Telephone and Telegraph
Company, 28 ends .(Owens Corning S-901, high glass filamentsl
were drawn through.the resin bath in spaced relatlon at
a speed of 10 feet per minute, and on leaving the resin
bath, were combined and passed through an aperture to
remove excess resine The fibers were then separated by
a spacing die having apertures with a spacing of one-
quarter inch between adjacent strands, and in this open
configuration the parallel strands were carried through
an 8-foot long preheating zone in spaced relation to the
internal surfaces of the preheating zone maintained at
127Ct
At the outer end o the preheating zone, the optical
. fiber was.introduced into the center of the group of
. reinforcing resin coated glass fibers, and the combined
fibers were drawn together and through five successive sizing dies
and heating chambers with the combined fibers in spaced relation
to the surfaces of the chambers. Each of the heating
chambers was 32 inches in length and was maintained at
a temperature of 182Ct At the end of this process, the
cured and finished, ruggedized optical fiber was wound on
4-foot diameter reel dri~en by a speed controlled pull-
through drive motor.
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