U.S. patent application number 14/111052 was filed with the patent office on 2014-02-06 for impregnation section of die and method for impregnating fiber rovings.
This patent application is currently assigned to Ticona LLC. The applicant listed for this patent is David W. Eastep, Aaron H. Johnson, Timothy A. Regan, Timothy L. Tibor. Invention is credited to David W. Eastep, Aaron H. Johnson, Timothy A. Regan, Timothy L. Tibor.
Application Number | 20140037842 14/111052 |
Document ID | / |
Family ID | 44625971 |
Filed Date | 2014-02-06 |
United States Patent
Application |
20140037842 |
Kind Code |
A1 |
Tibor; Timothy L. ; et
al. |
February 6, 2014 |
Impregnation Section of Die and Method for Impregnating Fiber
Rovings
Abstract
An impregnation section (150) and a method for impregnating
fiber rovings (142) with a polymer resin (214) are disclosed. The
impregnation section (150) includes an impregnation zone (250) and
a gate passage (270). The impregnation zone (250) is configured to
impregnate the plurality of rovings (142) with the resin (214). The
gate passage (270) is in fluid communication with the impregnation
zone (250) for flowing the resin therethrough such that the resin
impinges on a surface (216) of each of the plurality of rovings
(142) facing the gate passage (270) and substantially uniformly
coats the plurality of rovings. The method includes impinging a
polymer resin (214) onto a surface of a plurality of fiber rovings
(142), and substantially uniformly coating the plurality of rovings
with the resin. The method further includes traversing the
plurality of coated rovings through an impregnation zone (250).
Each of the plurality of rovings (142) is under a tension of from
about 5 Newtons to about 300 Newtons within the impregnation zone
(250).
Inventors: |
Tibor; Timothy L.; (Winona,
MN) ; Regan; Timothy A.; (Winona, MN) ;
Johnson; Aaron H.; (Winona, MN) ; Eastep; David
W.; (Winona, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tibor; Timothy L.
Regan; Timothy A.
Johnson; Aaron H.
Eastep; David W. |
Winona
Winona
Winona
Winona |
MN
MN
MN
MN |
US
US
US
US |
|
|
Assignee: |
Ticona LLC
Florence
KY
|
Family ID: |
44625971 |
Appl. No.: |
14/111052 |
Filed: |
April 12, 2011 |
PCT Filed: |
April 12, 2011 |
PCT NO: |
PCT/US11/32080 |
371 Date: |
October 10, 2013 |
Current U.S.
Class: |
427/175 ;
118/423 |
Current CPC
Class: |
D06B 3/04 20130101; B29C
70/523 20130101; B29B 15/122 20130101; B29C 70/526 20130101 |
Class at
Publication: |
427/175 ;
118/423 |
International
Class: |
D06B 3/04 20060101
D06B003/04 |
Claims
1. An impregnation section of a die for impregnating a plurality of
fiber rovings with a polymer resin, the impregnation section
comprising: an impregnation zone configured to impregnate the
plurality of rovings with the resin; and a gate passage in fluid
communication with the impregnation zone for flowing the resin
therethrough such that the resin impinges on a surface of each of
the plurality of rovings facing the gate passage and substantially
uniformly coats the plurality of rovings.
2. The impregnation section of claim 1, wherein the gate passage
extends vertically to the impregnation zone.
3. The impregnation section of claim 1, wherein at least a portion
of the gate passage has a decreasing cross-sectional profile in a
flow direction of the resin.
4. The impregnation section of claim 1, wherein the impregnation
zone comprises a plurality of contact surfaces.
5. The impregnation section of claim 4, wherein the impregnation
zone comprises between 2 and 50 contact surfaces.
6. The impregnation section of claim 4, wherein each of the
plurality of contact surfaces comprises a curvilinear contact
surface.
7. The impregnation section of claim 4, wherein each of the
plurality of contact surfaces is configured such that the plurality
of rovings traverse the contact surface at an angle in the range
between 1 degree and 30 degrees.
8. The impregnation section of claim 1, wherein the impregnation
zone has a waveform cross-sectional profile.
9. The impregnation section of claim 1, wherein the impregnation
zone comprises a plurality of pins.
10. The impregnation section of claim 9, wherein each of the
plurality of pins is static.
11. The impregnation section of claim 9, wherein each of the
plurality of pins is rotationally driven.
12. The impregnation section of claim 1, further comprising a first
plate defining a first inner surface and a second plate spaced
apart from the first plate and defining a second opposing inner
surface, wherein the impregnation zone is defined between the first
plate and the second plate, and wherein the impregnation zone
comprises a plurality of contact surfaces defined on only one of
the first inner surface or the second inner surface.
13. The impregnation section of claim 1, further comprising a land
zone downstream of the impregnation zone in a run direction of the
plurality of rovings.
14. The impregnation section of claim 13, wherein at least a
portion of the land zone has an increasing cross-sectional profile
in the run direction.
15. The impregnation section of claim 1, further comprising a
faceplate adjoining the impregnation zone, the faceplate configured
to meter excess resin within the plurality of rovings.
16. The impregnation section of any of claim 1, wherein the resin
is a thermoplastic resin.
17. The impregnation section of claim 1, wherein the resin is a
thermoset resin.
18. A method for impregnating a plurality of fiber rovings with a
polymer resin, the method comprising: impinging a polymer resin
onto a surface of a plurality of fiber rovings, substantially
uniformly coating the plurality of rovings with the resin; and
traversing the plurality of coated rovings through an impregnation
zone to impregnate the plurality of coated rovings with the resin,
wherein each of the plurality of rovings is under a tension of from
about 5 Newtons to about 300 Newtons within the impregnation
zone.
19. The method of claim 18, further comprising flowing the resin
through a gate passage, and wherein at least a portion of the gate
passage has a decreasing cross-sectional profile in a flow
direction of the resin.
20. The method of claim 18, wherein the plurality of rovings
traverse from the impregnation zone through a land zone, the land
zone positioned downstream of the impregnation zone in a run
direction of the plurality of rovings.
Description
BACKGROUND OF THE INVENTION
[0001] Fiber rovings have been employed in a wide variety of
applications. For example, such rovings have been utilized to form
fiber-reinforced composite rods. The rods may be utilized as
lightweight structural reinforcements. For example, power
umbilicals are often used in the transmission of fluids and/or
electric signals between the sea surface and equipment located on
the sea bed. To help strengthen such umbilicals, attempts have been
made to use pultruded carbon fiber rods as separate load carrying
elements.
[0002] Another application that is particularly suited for the use
of fiber rovings is in the formation of profiles. Profiles are
pultruded parts with a wide variety of cross-sectional shapes, and
may be employed as a structural member for window lineals, decking
planks, railings, balusters, roofing tiles, siding, trim boards,
pipe, fencing, posts, light posts, highway signage, roadside marker
posts, etc. Hollow profiles have been formed by pulling
("pultruding") continuous fiber rovings through a resin and then
shaping the fiber-reinforced resin within a pultrusion die.
[0003] Further, fiber rovings may generally be utilized in any
suitable applications to form, for example, suitable fiber
reinforced plastics. As is generally known in the art, rovings
utilized in these applications are typically combined with a
polymer resin.
[0004] There are many significant problems, however, with currently
known rovings and the resulting applications that utilize such
rovings. For example, many rovings rely upon thermoset resins
(e.g., vinyl esters) to help achieve desired strength properties.
Thermoset resins are difficult to use during manufacturing and do
not possess good bonding characteristics for forming layers with
other materials. Further, attempts have been made to form rovings
from thermoplastic polymers in other types of applications. U.S.
Patent Publication No. 2005/0186410 to Bryant, et al., for
instance, describes attempts that were made to embed carbon fibers
into a thermoplastic resin to form a composite core of an
electrical transmission cable. Unfortunately, Bryant, et al. notes
that these cores exhibited flaws and dry spots due to inadequate
wetting of the fibers, which resulted in poor durability and
strength. Another problem with such cores is that the thermoplastic
resins could not operate at a high temperature.
[0005] As such, a need currently exists for an improved
impregnation section of a die and method for impregnating a fiber
roving. Specifically, a need currently exists for an impregnation
section and method that produce fiber rovings which provide the
desired strength, durability, and temperature performance demanded
by a particular application.
SUMMARY OF THE INVENTION
[0006] In accordance with one embodiment of the present invention,
an impregnation section of a die is disclosed for impregnating a
plurality of fiber rovings with a polymer resin. The impregnation
section includes an impregnation zone and a gate passage. The
impregnation zone is configured to impregnate the plurality of
rovings with the resin. The gate passage is in fluid communication
with the impregnation zone for flowing the resin therethrough such
that the resin impinges on a surface of each of the plurality of
rovings facing the gate passage and substantially uniformly coats
the plurality of rovings.
[0007] In accordance with another embodiment of the present
invention, a method is disclosed for impregnating a plurality of
fiber rovings with a polymer resin. The method includes impinging a
polymer resin onto a surface of a plurality of fiber rovings, and
substantially uniformly coating the plurality of rovings with the
resin. The method further includes traversing the plurality of
coated rovings through an impregnation zone to impregnate the
plurality of coated rovings with the resin. Each of the plurality
of rovings is under a tension of from about 5 Newtons to about 300
Newtons within the impregnation zone.
[0008] Other features and aspects of the present invention are set
forth in greater detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] A full and enabling disclosure of the present invention,
including the best mode thereof to one skilled in the art, is set
forth more particularly in the remainder of the specification,
including reference to the accompanying figures, in which:
[0010] FIG. 1 is a schematic illustration of one embodiment of an
impregnation system for use in the present invention;
[0011] FIG. 2 is a perspective view of one embodiment of a die for
use in the present invention;
[0012] FIG. 3 is an opposing perspective view of one embodiment of
a die for use in the present invention;
[0013] FIG. 4 is a cross-sectional view of the die shown in FIG.
2;
[0014] FIG. 5 is an exploded view of one embodiment of a manifold
assembly and gate passage for a die that may be employed in the
present invention;
[0015] FIG. 6 is a plan view of one embodiment of a manifold
assembly that may be employed in the present invention;
[0016] FIG. 7 is a plan view of another embodiment of a manifold
assembly that may be employed in the present invention;
[0017] FIG. 8 is a plan view of another embodiment of a manifold
assembly that may be employed in the present invention;
[0018] FIG. 9 is a plan view of another embodiment of a manifold
assembly that may be employed in the present invention;
[0019] FIG. 10 is a plan view of another embodiment of a manifold
assembly that may be employed in the present invention;
[0020] FIG. 11 is a plan view of another embodiment of a manifold
assembly that may be employed in the present invention;
[0021] FIG. 12 is a perspective view of one embodiment of a plate
at least partially defining an impregnation zone that may be
employed in the present invention;
[0022] FIG. 13 is a close-up cross-sectional view, as indicated in
FIG. 4, of one embodiment of a portion of an impregnation zone that
may be employed in the present invention;
[0023] FIG. 14 is a close-up cross-sectional view of another
embodiment of a portion of an impregnation zone that may be
employed in the present invention;
[0024] FIG. 15 is a close-up cross-sectional view of another
embodiment of a portion of an impregnation zone that may be
employed in the present invention;
[0025] FIG. 16 is a close-up cross-sectional view of another
embodiment of a portion of an impregnation zone that may be
employed in the present invention;
[0026] FIG. 17 is a close-up cross-sectional view of another
embodiment of a portion of an impregnation zone that may be
employed in the present invention;
[0027] FIG. 18 is a perspective view of one embodiment of a land
zone that may be employed in the present invention;
[0028] FIG. 19 is a perspective view of another embodiment of a
land zone that may be employed in the present invention;
[0029] FIG. 20 is a perspective view of one embodiment of a
consolidated ribbon for use in the present invention; and
[0030] FIG. 21 is a cross-sectional view of the ribbon shown in
FIG. 20.
[0031] Repeat use of reference characters in the present
specification and drawings is intended to represent the same or
analogous features or elements of the present invention.
DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS
[0032] It is to be understood by one of ordinary skill in the art
that the present discussion is a description of exemplary
embodiments only, and is not intended as limiting the broader
aspects of the present invention.
[0033] Generally speaking, the present invention is directed to an
impregnation section of a die and a method for impregnating fiber
rovings with a polymer resin. The impregnated fiber rovings may be
utilized in composite rods, profiles, or any other suitable fiber
reinforced plastic applications. The impregnation section according
to the present invention generally includes an impregnation zone
and a gate passage. Resin is flowed through the gate passage, which
is in fluid communication with the impregnation zone. The rovings
are traversed through the die such that the resin, upon exiting the
gate passage, impinges on a surface of the rovings facing the gate
passage and substantially uniformly coats the rovings. After being
coated with the resin, the rovings are traversed through the
impregnation zone and impregnated therein with the resin.
[0034] According to further aspects of the present invention, an
extrusion device may be employed in conjunction with the die to
impregnate the rovings with the polymer. Among other things, the
extrusion device further facilitates the ability of the polymer to
be applied to the entire surface of the fibers, as discussed
below.
[0035] Referring to FIG. 1, one embodiment of such an extrusion
device is shown. More particularly, the apparatus includes an
extruder 120 containing a screw shaft 124 mounted inside a barrel
122. A heater 130 (e.g., electrical resistance heater) is mounted
outside the barrel 122. During use, a polymer feedstock 127 is
supplied to the extruder 120 through a hopper 126. The feedstock
127 is conveyed inside the barrel 122 by the screw shaft 124 and
heated by frictional forces inside the barrel 122 and by the heater
130. Upon being heated, the feedstock 127 exits the barrel 122
through a barrel flange 128 and enters a die flange 132 of an
impregnation die 150.
[0036] A continuous fiber roving 142 or a plurality of continuous
fiber rovings 142 are supplied from a reel or reels 144 to die 150.
The rovings 142 are generally positioned side-by-side, with minimal
to no distance between neighboring rovings, before impregnation.
The feedstock 127 may further be heated inside the die by heaters
133 mounted in or around the die 150. The die is generally operated
at temperatures that are sufficient to cause and/or maintain the
proper melt temperature for the polymer, thus allowing for the
desired level of impregnation of the rovings by the polymer.
Typically, the operation temperature of the die is higher than the
melt temperature of the polymer, such as at temperatures from about
200.degree. C. to about 450.degree. C. When processed in this
manner, the continuous fiber rovings 142 become embedded in the
polymer matrix, which may be a resin 214 (FIG. 4) processed from
the feedstock 127. The mixture may then exit the impregnation die
150 as wetted composite or extrudate 152.
[0037] As used herein, the term "roving" generally refers to a
bundle of individual fibers. The fibers contained within the roving
can be twisted or can be straight. The rovings may contain a single
fiber type or different types of fibers. Different fibers may also
be contained in individual rovings or, alternatively, each roving
may contain a different fiber type. The continuous fibers employed
in the rovings possess a high degree of tensile strength relative
to their mass. For example, the ultimate tensile strength of the
fibers is typically from about 1,000 to about 15,000 Megapascals
("MPa"), in some embodiments from about 2,000 MPa to about 10,000
MPa, and in some embodiments, from about 3,000 MPa to about 6,000
MPa. Such tensile strengths may be achieved even though the fibers
are of a relatively light weight, such as a mass per unit length of
from about 0.05 to about 2 grams per meter, in some embodiments
from about 0.4 to about 1.5 grams per meter. The ratio of tensile
strength to mass per unit length may thus be about 1,000
Megapascals per gram per meter ("MPa/g/m") or greater, in some
embodiments about 4,000 MPa/g/m or greater, and in some
embodiments, from about 5,500 to about 20,000 MPa/g/m. Such high
strength fibers may, for instance, be metal fibers, glass fibers
(e.g., E-glass, A-glass, C-glass, D-glass, AR-glass, R-glass,
S1-glass, S2-glass, etc.), carbon fibers (e.g., amorphous carbon,
graphitic carbon, or metal-coated carbon, etc.), boron fibers,
ceramic fibers (e.g., alumina or silica), aramid fibers (e.g.,
Kevlar.RTM. marketed by E.I. duPont de Nemours, Wilmington, Del.),
synthetic organic fibers (e.g., polyamide, polyethylene,
paraphenylene, terephthalamide, polyethylene terephthalate and
polyphenylene sulfide), and various other natural or synthetic
inorganic or organic fibrous materials known for reinforcing
thermoplastic and/or thermoset compositions. Carbon fibers are
particularly suitable for use as the continuous fibers, which
typically have a tensile strength to mass ratio in the range of
from about 5,000 to about 7,000 MPa/g/m. The continuous fibers
often have a nominal diameter of about 4 to about 35 micrometers,
and in some embodiments, from about 9 to about 35 micrometers. The
number of fibers contained in each roving can be constant or vary
from roving to roving. Typically, a roving contains from about
1,000 fibers to about 50,000 individual fibers, and in some
embodiments, from about 5,000 to about 30,000 fibers.
[0038] Any of a variety of thermoplastic or thermoset polymers may
be employed to form the polymer matrix in which the continuous
fibers are embedded. For example, suitable thermoplastic polymers
for use in the present invention may include, for instance,
polyolefins (e.g., polypropylene, propylene-ethylene copolymers,
etc.), polyesters (e.g., polybutylene terephalate ("PBT")),
polycarbonates, polyamides (e.g., Nylon.TM.), polyether ketones
(e.g., polyetherether ketone ("PEEK")), polyetherimides,
polyarylene ketones (e.g., polyphenylene diketone ("PPDK")), liquid
crystal polymers, polyarylene sulfides (e.g., polyphenylene sulfide
("PPS"), poly(biphenylene sulfide ketone), poly(phenylene sulfide
diketone), poly(biphenylene sulfide), etc.), fluoropolymers (e.g.,
polytetrafluoroethylene-perfluoromethylvinylether polymer,
perfluoroalkoxyalkane polymer, petrafluoroethylene polymer,
ethylene-tetrafluoroethylene polymer, etc.), polyacetals,
polyurethanes, polycarbonates, styrenic polymers (e.g.,
acrylonitrile butadiene styrene ("ABS")), and so forth.
[0039] The properties of the polymer matrix are generally selected
to achieve the desired combination of processability and
performance. For example, the melt viscosity of the polymer matrix
is generally low enough so that the polymer can adequately
impregnate the fibers. In this regard, the melt viscosity typically
ranges from about 25 to about 1,000 Pascal-seconds ("Pa-s"), in
some embodiments from 50 about 500 Pa-s, and in some embodiments,
from about 60 to about 200 Pa-s, determined at the operating
conditions used for the polymer (e.g., about 360.degree. C.).
Likewise, when the impregnated rovings are intended for
applications involving high temperatures (e.g., high voltage
transmission cables), a polymer is employed that has a relatively
high melting temperature. For example, the melting temperature of
such high temperature polymers may range from about 200.degree. C.
to about 500.degree. C., in some embodiments from about 225.degree.
C. to about 400.degree. C., and in some embodiments, from about
250.degree. C. to about 350.degree. C.
[0040] Polyarylene sulfides are particularly suitable for use in
the present invention as a high temperature matrix with the desired
melt viscosity. Polyphenylene sulfide, for example, is a
semi-crystalline resin that generally includes repeating monomeric
units represented by the following general formula:
##STR00001##
[0041] These monomeric units typically constitute at least 80 mole
%, and in some embodiments, at least 90 mole %, of the recurring
units, in the polymer. It should be understood, however, the
polyphenylene sulfide may contain additional recurring units, such
as described in U.S. Pat. No. 5,075,381 to Gotoh, et al., which is
incorporated herein in its entirety by reference thereto for all
purposes. When employed, such additional recurring units typically
constitute no more than about 20 mole % of the polymer.
Commercially available high melt viscosity polyphenylene sulfides
may include those available from Ticona LLC (Florence, Ky.) under
the trade designation FORTRON.RTM.. Such polymers may have a
melting temperature of about 285.degree. C. (determined according
to ISO 11357-1,2,3) and a melt viscosity of from about 260 to about
320 Pascal-seconds at 310.degree. C.
[0042] A pressure sensor 137 (FIGS. 2 and 3) may sense the pressure
near the impregnation die 150 to allow control to be exerted over
the rate of extrusion by controlling the rotational speed of the
screw shaft 124, or the feed rate of the feeder. That is, the
pressure sensor 137 is positioned near the impregnation die 150,
such as upstream of the manifold assembly 220, so that the extruder
120 can be operated to deliver a correct amount of resin 214 for
interaction with the fiber rovings 142. After leaving the
impregnation die 150, the extrudate 152, or impregnated fiber
rovings 142, may enter an optional pre-shaping or guiding section
(not shown) before entering a nip formed between two adjacent
rollers 190. Although optional, the rollers 190 can help to
consolidate the extrudate 152 into the form of a ribbon, as well as
enhance fiber impregnation and squeeze out any excess voids. In
addition to the rollers 190, other shaping devices may also be
employed, such as a die system. Regardless, the resulting
consolidated ribbon 156 is pulled by tracks 162 and 164 mounted on
rollers. The tracks 162 and 164 also pull the extrudate 152 from
the impregnation die 150 and through the rollers 190. If desired,
the consolidated ribbon 156 may be wound up at a section 171.
Generally speaking, the resulting ribbons are relatively thin and
typically have a thickness of from about 0.05 to about 1
millimeter, in some embodiments from about 0.1 to about 0.8
millimeters, and in some embodiments, from about 0.2 to about 0.4
millimeters.
[0043] Perspective views of one embodiment of a die 150 according
to the present disclosure are further shown in FIGS. 2 and 3. As
shown, resin 214 is flowed into the die 150 as indicated by resin
flow direction 244. The resin 214 is distributed within the die 150
and then interacted with the rovings 142. The rovings 142 are
traversed through the die 150 in roving run direction 282, and are
coated with resin 214. The rovings 142 are then impregnated with
the resin 214, and these impregnated rovings 142 exit the die
150.
[0044] Within the impregnation die, it is generally desired that
the rovings 142 are traversed through an impregnation zone 250 to
impregnate the rovings with the polymer resin 214. In the
impregnation zone 250, the polymer resin may be forced generally
transversely through the rovings by shear and pressure created in
the impregnation zone 250, which significantly enhances the degree
of impregnation. This is particularly useful when forming a
composite from ribbons of a high fiber content, such as about 35%
weight fraction ("Wf") or more, and in some embodiments, from about
40% Wf or more. Typically, the die 150 will include a plurality of
contact surfaces 252, such as for example at least 2, at least 3,
from 4 to 7, from 2 to 20, from 2 to 30, from 2 to 40, from 2 to
50, or more contact surfaces 252, to create a sufficient degree of
penetration and pressure on the rovings 142. Although their
particular form may vary, the contact surfaces 252 typically
possess a curvilinear surface, such as a curved lobe, pin, etc. The
contact surfaces 252 are also typically made of a metal
material.
[0045] FIG. 4 shows a cross-sectional view of an impregnation die
150. As shown, the impregnation die 150 may include a manifold
assembly 220 and an impregnation section. The impregnation section
includes a gate passage 270 and an impregnation zone 250. The
manifold assembly 220 is provided for flowing the polymer resin 214
therethrough. For example, the manifold assembly 220 may include a
channel 222 or a plurality of channels 222. The resin 214 provided
to the impregnation die 150 may flow through the channels 222.
[0046] As shown in FIGS. 5 through 11, in exemplary embodiments, at
least a portion of each of the channels 222 may be curvilinear. The
curvilinear portions may allow for relatively smooth redirection of
the resin 214 in various directions to distribute the resin 214
through the manifold assembly 220, and may allow for relatively
smooth flow of the resin 214 through the channels 222.
Alternatively, the channels 222 may be linear, and redirection of
the resin 214 may be through relatively sharp transition areas
between linear portions of the channels 222. It should further be
understood that the channels 222 may have any suitable shape, size,
and/or contour.
[0047] The plurality of channels 222 may, in exemplary embodiments
as shown in FIGS. 5 through 11, be a plurality of branched runners
222. The runners 222 may include a first branched runner group 232.
The first branched runner group 232 includes a plurality of runners
222 branching off from an initial channel or channels 222 that
provide the resin 214 to the manifold assembly 220. The first
branched runner group 232 may include 2, 3, 4 or more runners 222
branching off from the initial channels 222.
[0048] If desired, the runners 222 may include a second branched
runner group 234 diverging from the first branched runner group
232, as shown in FIGS. 5 and 7 through 11. For example, a plurality
of runners 222 from the second branched runner group 234 may branch
off from one or more of the runners 222 in the first branched
runner group 232. The second branched runner group 234 may include
2, 3, 4 or more runners 222 branching off from runners 222 in the
first branched runner group 232.
[0049] If desired, the runners 222 may include a third branched
runner group 236 diverging from the second branched runner group
234, as shown in FIGS. 5 and 8 through 9. For example, a plurality
of runners 222 from the third branched runner group 236 may branch
off from one or more of the runners 222 in the second branched
runner group 234. The third branched runner group 236 may include
2, 3, 4 or more runners 222 branching off from runners 222 in the
second branched runner group 234.
[0050] In some exemplary embodiments, as shown in FIGS. 5 through
11, the plurality of branched runners 222 have a symmetrical
orientation along a central axis 224. The branched runners 222 and
the symmetrical orientation thereof generally evenly distribute the
resin 214, such that the flow of resin 214 exiting the manifold
assembly 220 and coating the rovings 142 is substantially uniformly
distributed on the rovings 142. This desirably allows for generally
uniform impregnation of the rovings 142.
[0051] Further, the manifold assembly 220 may in some embodiments
define an outlet region 242. The outlet region 242 is that portion
of the manifold assembly 220 wherein resin 214 exits the manifold
assembly 220. Thus, the outlet region 242 generally encompasses at
least a downstream portion of the channels or runners 222 from
which the resin 214 exits. In some embodiments, as shown in FIGS. 5
through 10, at least a portion of the channels or runners 222
disposed in the outlet region 242 have an increasing area in a flow
direction 244 of the resin 214. The increasing area allows for
diffusion and further distribution of the resin 214 as the resin
214 flows through the manifold assembly 220, which further allows
for substantially uniform distribution of the resin 214 on the
rovings 142. Additionally or alternatively, various channels or
runners 222 disposed in the outlet region 242 may have constant
areas in the flow direction 244 of the resin 214, as shown in FIG.
11, or may have decreasing areas in the flow direction 244 of the
resin 214.
[0052] In some embodiments, as shown in FIGS. 5 through 9, each of
the channels or runners 222 disposed in the outlet region 242 is
positioned such that resin 214 flowing therefrom is combined with
resin 214 from other channels or runners 222 disposed in the outlet
region 242. This combination of the resin 214 from the various
channels or runners 222 disposed in the outlet region 242 produces
a generally singular and uniformly distributed flow of resin 214
from the manifold assembly 220 to substantially uniformly coat the
rovings 142. Alternatively, as shown in FIGS. 10 and 11, various of
the channels or runners 222 disposed in the outlet region 242 may
be positioned such that resin 214 flowing therefrom is discrete
from the resin 214 from other channels or runners 222 disposed in
the outlet region 242. In these embodiments, a plurality of
discrete but generally evenly distributed resin flows 214 may be
produced by the manifold assembly 220 for substantially uniformly
coating the rovings 142.
[0053] As shown in FIG. 4, at least a portion of the channels or
runners 222 disposed in the outlet region 242 have curvilinear
cross-sectional profiles. These curvilinear profiles allow for the
resin 214 to be gradually directed from the channels or runners 222
generally downward towards the rovings 142. Alternatively, however,
these channels or runners 222 may have any suitable cross-sectional
profiles.
[0054] It should be understood that the present disclosure is not
limited to the above disclosed embodiments of the manifold assembly
220. Rather, any suitable manifold assembly 220 is within the scope
and spirit of the present disclosure. In particular, manifold
assemblies 220 which may provide generally even, uniform
distribution of resin 214, such as coat-hanger, horseshoe,
flex-lip, or adjustable slot manifold assemblies, are within the
scope and spirit of the present disclosure.
[0055] As further illustrated in FIGS. 4 and 5, after flowing
through the manifold assembly 220, the resin 214 may flow through
gate passage 270. Gate passage 270 is positioned between the
manifold assembly 220 and the impregnation zone 250, and is
provided for flowing the resin 214 from the manifold, assembly 220
such that the resin 214 coats the rovings 142. Thus, resin 214
exiting the manifold assembly 220, such as through outlet region
242, may enter gate passage 270 and flow therethrough.
[0056] In some embodiments, as shown in FIG. 4, the gate passage
270 extends vertically between the manifold assembly 220 and the
impregnation zone 250. Alternatively, however, the gate passage 270
may extend at any suitable angle between vertical and horizontal
such that resin 214 is allowed to flow therethrough.
[0057] Further, as shown in FIG. 4, in some embodiments at least a
portion of the gate passage 270 has a decreasing cross-sectional
profile in the flow direction 244 of the resin 214. This taper of
at least a portion of the gate passage 270 may increase the flow
rate of the resin 214 flowing therethrough before it contacts the
rovings 142, which may allow the resin 214 to impinge on the
rovings 142. Initial impingement of the rovings 142 by the resin
214 provides for further impregnation of the rovings, as discussed
below. Further, tapering of at least a portion of the gate passage
270 may increase backpressure in the gate passage 270 and the
manifold assembly 220, which may further provide more even, uniform
distribution of the resin 214 to coat the rovings 142.
Alternatively, the gate passage 270 may have an increasing or
generally constant cross-sectional profile, as desired or
required.
[0058] Upon exiting the manifold assembly 220 and the gate passage
270 of the die 150 as shown in FIG. 6, the resin 214 contacts the
rovings 142 being traversed through the die 150. As discussed
above, the resin 214 may substantially uniformly coat the rovings
142, due to distribution of the resin 214 in the manifold assembly
220 and the gate passage 270. Further, in some embodiments as shown
in FIGS. 13 through 17, the resin 214 may impinge on an upper
surface 216 or surface 216 facing gate passage 270 of each of the
rovings 142, or on a lower surface of each of the rovings 142, or
on both an upper and lower surface of each of the rovings 142.
Initial impingement on the rovings 142 provides for further
impregnation of the rovings 142 with the resin 214. Impingement on
the rovings 142 may be facilitated by the velocity of the resin 214
when it impacts the rovings 142, the proximity of the rovings 142
to the resin 214 when the resin exits the manifold assembly 220 or
gate passage 270, or other various variables.
[0059] As shown in FIG. 4, the coated rovings 142 are traversed in
run direction 282 through impregnation zone 250. The impregnation
zone 250 is in fluid communication with the manifold assembly 220,
such as through the gate passage 270 disposed therebetween. The
impregnation zone 250 is configured to impregnate the rovings 142
with the resin 214.
[0060] For example, as discussed above, in exemplary embodiments as
shown in FIGS. 4 and 12 through 17, the impregnation zone 250
includes a plurality of contact surfaces 252. The rovings 142 are
traversed over the contact surfaces 252 in the impregnation zone.
Impingement of the rovings 142 on the contact surface 252 creates
shear and pressure sufficient to impregnate the rovings 142 with
the resin 214 coating the rovings 142.
[0061] In some embodiments, as shown in FIGS. 4 and 13 through 17,
the impregnation zone 250 is defined between two spaced apart
opposing plates 256 and 258. First plate 256 defines a first inner
surface 257, while second plate 258 defines a second inner surface
259. The impregnation zone 250 is defined between the first plate
256 and the second plate 258. The contact surfaces 252 may be
defined on or extend from both the first and second inner surfaces
257 and 259, or only one of the first and second inner surfaces 257
and 259.
[0062] In exemplary embodiments, as shown in FIGS. 4, 13, and 15
through 17, the contact surfaces 252 may be defined alternately on
the first and second surfaces 257 and 259 such that the rovings
alternately impinge on contact surfaces 252 on the first and second
surfaces 257 and 259. Thus, the rovings 142 may pass contact
surfaces 252 in a waveform, tortuous or sinusoidual-type pathway,
which enhances shear.
[0063] Angle 254 at which the rovings 142 traverse the contact
surfaces 252 may be generally high enough to enhance shear and
pressure, but not so high to cause excessive forces that will break
the fibers. Thus, for example, the angle 254 may be in the range
between approximately 1.degree. and approximately 30.degree., and
in some embodiments, between approximately 5.degree. and
approximately 25.degree..
[0064] As stated above, contact surfaces 252 typically possess a
curvilinear surface, such as a curved lobe, pin, etc. Further, in
many exemplary embodiments, the impregnation zone 250 has a
waveform cross-sectional profile. In one exemplary embodiment as
shown in FIGS. 4, 12 and 13, the contact surfaces 252 are lobes
that form portions of the waveform surfaces of both the first and
second plates 256 and 258 and define the waveform cross-sectional
profile. FIG. 12 illustrates the second plate 258 and the various
contact surfaces thereon that form at least a portion of the
impregnation zone 250 according to these embodiments.
[0065] In other embodiments, as shown in FIG. 14, the contact
surfaces 252 are lobes that form portions of a waveform surface of
only one of the first or second plate 256 or 258. In these
embodiments, impingement occurs only on the contact surfaces 252 on
the surface of the one plate. The other plate may generally be flat
or otherwise shaped such that no interaction with the coated
rovings occurs.
[0066] In other alternative embodiments, as shown in FIGS. 15
through 17, the impregnation zone 250 may include a plurality of
pins (or rods) 260, each pin having a contact surface 252. The pins
260 may be static, as shown in FIGS. 15 and 16, freely rotational
(not shown), or rotationally driven, as shown in FIG. 17. Further,
the pins 260 may be mounted directly to the surface of the plates
defining the impingement zone, as shown in FIG. 15, or may be
spaced from the surface as shown in FIGS. 16 and 17. It should be
noted that the pins 260 may be heated by heaters 133, or may be
heated individually or otherwise as desired or required. Further,
the pins 260 may be contained within the die 150, or may extend
outwardly from the die 150 and not be fully encased therein.
[0067] In further alternative embodiments, the contact surfaces 252
and impregnation zone 250 may comprise any suitable shapes and/or
structures for impregnating the rovings 142 with the resin 214 as
desired or required.
[0068] To further facilitate impregnation of the rovings 142, they
may also be kept under tension while present within the die 150,
and specifically within the impregnation zone 250. The tension may,
for example, range from about 5 to about 300 Newtons, in some
embodiments from about 50 to about 250 Newtons, and in some
embodiments, from about 100 to about 200 Newtons per roving 142 or
tow of fibers.
[0069] As shown in FIG. 4 and FIGS. 18 and 19, in some embodiments,
a land zone 280 may be positioned downstream of the impregnation
zone 250 in run direction 282 of the rovings 142. The rovings 142
may traverse through the land zone 280 before exiting the die 150.
In some embodiments, as shown in FIG. 18, at least a portion of the
land zone 280 may have an increasing cross-sectional profile in run
direction 282, such that the area of the land zone 280 increases.
The increasing portion may be the downstream portion of the land
zone 280 to facilitate the rovings 142 exiting the die 150.
Alternatively, the cross-sectional profile or any portion thereof
may decrease, or may remain constant as shown in FIG. 19.
[0070] As further shown in FIG. 4, in some embodiments, a faceplate
290 may adjoin the impregnation zone 250. The faceplate 290 may be
positioned downstream of the impregnation zone 250 and, if
included, the land zone 280, in the run direction 282. Faceplate
290 is generally configured to meter excess resin 214 from the
rovings 142. Thus, apertures in the faceplate 290, through which
the rovings 142 traverse, may be sized such that when the rovings
142 are traversed therethrough, the size of the apertures causes
excess resin 214 to be removed from the rovings 142.
[0071] Additionally, other components may be optionally employed to
assist in the impregnation of the fibers. For example, a "gas jet"
assembly may be employed in certain embodiments to help uniformly
spread a roving of individual fibers, which may each contain up to
as many as 24,000 fibers, across the entire width of the merged
tow. This helps achieve uniform distribution of strength
properties. Such an assembly may include a supply of compressed air
or another gas that impinges in a generally perpendicular fashion
on the moving rovings that pass across exit ports. The spread
rovings may then be introduced into a die for impregnation, such as
described above.
[0072] The impregnated rovings that result from use of the die and
method according to the present disclosure may have a very low void
fraction, which helps enhance their strength. For instance, the
void fraction may be about 3% or less, in some embodiments about 2%
or less, in some embodiments about 1% or less, and in some
embodiments, about 0.5% or less. The void fraction may be measured
using techniques well known to those skilled in the art. For
example, the void fraction may be measured using a "resin burn off"
test in which samples are placed in an oven (e.g., at 600.degree.
C. for 3 hours) to burn out the resin. The mass of the remaining
fibers may then be measured to calculate the weight and volume
fractions. Such "burn off" testing may be performed in accordance
with ASTM D 2584-08 to determine the weights of the fibers and the
polymer matrix, which may then be used to calculate the "void
fraction" based on the following equations:
V.sub.f=100*(.rho..sub.t-.rho..sub.c)/.rho..sub.t
where,
[0073] V.sub.f is the void fraction as a percentage;
[0074] .rho..sub.c is the density of the composite as measured
using known techniques, such as with a liquid or gas pycnometer
(e.g., helium pycnometer);
[0075] .rho..sub.t is the theoretical density of the composite as
is determined by the following equation:
.rho..sub.t=1/[W.sub.f/.rho..sub.f+W.sub.m/.rho..sub.m]
[0076] .rho..sub.m is the density of the polymer matrix (e.g., at
the appropriate crystallinity);
[0077] .rho..sub.f is the density of the fibers;
[0078] W.sub.f is the weight fraction of the fibers; and
[0079] W.sub.m is the weight fraction of the polymer matrix.
[0080] Alternatively, the void fraction may be determined by
chemically dissolving the resin in accordance with ASTM D 3171-09.
The "burn off" and "dissolution" methods are particularly suitable
for glass fibers, which are generally resistant to melting and
chemical dissolution. In other cases, however, the void fraction
may be indirectly calculated based on the densities of the polymer,
fibers, and ribbon in accordance with ASTM D 2734-09 (Method A),
where the densities may be determined ASTM D792-08 Method A. Of
course, the void fraction can also be estimated using conventional
microscopy equipment.
[0081] The present disclosure is further directed to a method for
impregnating at least one fiber roving 142 or a plurality of fiber
rovings 142 with a polymer resin 214. The method includes impinging
a polymer resin 214 onto a surface 216 of a plurality of fiber
rovings 142, and substantially uniformly coating the plurality of
rovings 142 with the resin 214, as discussed above. The method
further includes traversing the plurality of coated rovings 142
through an impregnation zone 250 to impregnate the plurality of
coated rovings 142 with the resin 214, as discussed above.
[0082] In some embodiments, the method may further include flowing
the resin 214 through a gate passage 270, as discussed above.
Further, the method may include traversing the rovings 142 from the
impregnation zone 250 through a land zone 280 and/or traversing the
rovings 142 through a faceplate 290, as discussed above.
[0083] As discussed above, after exiting the impregnation die 150,
the impregnated rovings 142, or extrudate 152, may be consolidated
into the form of a ribbon. The number of rovings employed in each
ribbon may vary. Typically, however, a ribbon will contain from 2
to 20 rovings, and in some embodiments from 2 to 10 rovings, and in
some embodiments, from 3 to 5 rovings. In some embodiments, it may
be desired that the rovings are spaced apart approximately the same
distance from each other within the ribbon. Referring to FIGS. 20
and 21, for example, one embodiment of a consolidated ribbon 4 is
shown that contains three (3) rovings 5 spaced equidistant from
each other in the -x direction.
[0084] A pultrusion process may further be utilized according to
the present disclosure for certain particular applications. For
example, in some embodiments, such process may be utilized to form
a rod. In these embodiments, continuous fibers of rovings 142 may
be oriented in the longitudinal direction (the machine direction
"A" of the system of FIG. 1) to enhance tensile strength. Besides
fiber orientation, other aspects of the pultrusion process may be
controlled to achieve the desired strength. For example, a
relatively high percentage of continuous fibers are employed in the
consolidated ribbon to provide enhanced strength properties. For
instance, continuous fibers typically constitute from about 25 wt.
% to about 80 wt. %, in some embodiments from about 30 wt. % to
about 75 wt. %, and in some embodiments, from about 35 wt. % to
about 60 wt. % of the ribbon. Likewise, polymer(s) typically
constitute from about 20 wt. % to about 75 wt. %, in some
embodiments from about 25 wt. % to about 70 wt. %, and in some
embodiments, from about 40 wt. % to about 65 wt. % of the
ribbon.
[0085] In general, ribbons may be supplied to the pultrusion system
directly from impregnation die 150, or may be supplied from
spindles or other suitable storage apparatus. A tension-regulating
device may be employed to help control the degree of tension in the
ribbons as they are drawn through the pultrusion system. An oven
may be supplied in the device for heating the ribbons. The ribbons
may then be provided to a consolidation die, which may operate to
compress the ribbons together into a preform, and to align and form
the initial shape of the desired product, such as a rod. If
desired, a second die (e.g., calibration die) may also be employed
that compresses the preform into a final shape. Cooling systems may
additionally be incorporated between the dies and/or after either
die. A downstream pulling device may be positioned to pull products
through the system.
[0086] These and other modifications and variations of the present
invention may be practiced by those of ordinary skill in the art,
without departing from the spirit and scope of the present
invention. In addition, it should be understood that aspects of the
various embodiments may be interchanged both in whole or in part.
Furthermore, those of ordinary skill in the art will appreciate
that the foregoing description is by way of example only, and is
not intended to limit the invention so further described in such
appended claims.
* * * * *