Note: Descriptions are shown in the official language in which they were submitted.
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GLASS FIBER BUNDLES FOR MAT APPLICATIONS
AND METHODS OF MAKING THE SAME
TECHNICAL FIELD AND INDUSTRIAL
APPLICABILITY OF THE INVENTION
The present invention relates generally to non-woven fibrous mats, and more
particularly, to dried bundles of chopped glass fibers that may be used as a
replacement for
glass forms conventionally utilized in mat forming applications, and even more
particularly, to wet-laid mat forming applications. Methods of forming the
dried bundles
of chopped glass fibers are also provided.
BACKGROUND OF THE INVENTION
Typically, glass fibers are fonned by drawing molten glass into filaments
througli a
bushing or orifice plate and applying an aqueous sizing composition containing
lubricants,
coupling agents, and film-forming binder resins to the filaments. The sizing
composition
provides protection to the fibers from interfilament abrasion and promotes
compatibility
between the glass fibers and the matrix in which the glass fibers are to be
used. After the
sizing composition is applied, the wet fibers may be gathered into one or more
strands,
chopped, and collected. The chopped strands inay contain hundreds or thousands
of
individual glass fibers. The collected chopped glass strands may then be
packaged in their
wet condition as wet chopped fiber strands (WUCS) or dried to form dry chopped
fiber
strands (DUCS).
Wet chopped fibers are conventionally used in wet-laid processes in which the
wet
clzopped fibers are dispersed in a water slurry that contains surfactants,
viscosity modifiers,
defoaming agents, and/or other chemical agents. The slurry containing the
chopped fibers
is then agitated so that the fibers become dispersed throughout the slurry.
The slurry
containing the fibers is deposited onto a moving screen wliere a substantial
portion of the
water is removed to form a web. A binder is then applied, and the resulting
mat is dried to
remove any remaining water and cure the binder. The formed non-woven mat is an
assembly of dispersed, individual glass filaments.
Dried chopped strands are commonly used in dry-laid processes in which the
dried
strands are air blown onto a conveyor or screen and consolidated to form a
mat. For
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example, dry chopped strands are suspended in air, collected as a loose web on
a screen or
perforated conveyor, and then consolidated to form a mat of randomly oriented
bundles.
Fibrous mats formed by wet-laid and dry-laid processes are extremely suitable
as
reinforcements for many types of applications. In order for the final laminate
to achieve
acceptable mechanical performance, it must include a sufficient amount by
weight of glass
reinforcements. Although the bundles of fibers present in the dry-laid mats
provide for a
high glass content, manufacturing dry chopped strands is expensive because
such strands
are generally dried and packaged in separate steps before being chopped. Thus,
it would
be desirable to utilize a less expensive glass formation platform that would
achieve the
increased glass content in composites that require a high impact strength.
Bundles of dried chopped fibers have previously been manufactured. Some
examples of the processes of forming these bundles of dried chopped fibers are
described
below.
U.S. Patent No. 4,024,647 to Schaefer discloses a method and apparatus for
drying
and conveying chopped glass strands. Glass filaments are attenuated through
orifices in a
bushing and coated with a lubricant binder and/or size. The filaments are
gathered into
one or more strands and chopped. The wet, chopped fibers then falls onto a
first vibratory
conveyor. The vibrations of the first vibratory conveyor maintains the chopped
strands in
fiber bundles by keeping the bundles from adhering to each other. The cliopped
strands
are then passed to a second vibratory conveyor and through a heating zone
where the
chopped strands are heated to reduce the moisture content to less than 0.1
percent by
weight. Chopped strands of a desired length then pass through a foraminous
portion of the
second vibratory conveyor and into a collection package.
U.S. Patent No. 5,055,119 to Flautt et cal. describe an energy efficient
process and
apparatus for forming glass fiber bundles or strands. Glass fibers are formed
from molten
glass discharged from a heated bushing. The fibers are moved downwardly and a
sizing is
applied to the glass fibers by an applicator. To dry the glass fibers, air
from around the
bushing is passed beneath the bushing where it is heated by the heat of the
bushing. The
heated air is drawn into a chamber through which the glass fibers pass. The
heat transfer
contact causes the water or solvent in the sizing composition to be
evaporated. The dried
fibers are then gathered into a bundle. The bundles may subsequently be
chopped.
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U.S. Patent No. 6,148,641 to Blough et al. describe a method and an apparatus
for
producing dried, chopped strands from a stipply of continuous fiber strands.
In the
described method, chopped fiber strands are produced from one or more
continuous
strands by chopping the fiber strands in a chopping assembly, ejecting the
chopped strands
from an exit asseinbly into a transition chtite directly into a drying
chamber, collecting the
chopped strands in the drying chamber, and at least partially drying the
strands in the
drying chamber.
In addition, chopped strand glass mats have been formed that contaiil glass
bundles, such as is found in dry-laid processes, and individual fibers such as
are found in
wet-laid processes, by utilizing wet-laid processes. Some examples of these
mats are set
forth below.
U.S. Patent Nos. 4,112,174 and 4,129,674 to Hannes et al. disclose glass mats
that
are formed of a web of monofilament fibers and elongated glass fiber bundles
interspersed
throughout the web in a randomly oriented pattern. The glass fiber bundles
preferably
contain from about 20 - 300 monofilaments. The fibrous mats are formed by wet-
laid
processes. To keep the glass fiber bundles in a bundle form in the slurry
during the mat
forming process, the bundles are coated with a water or other such liquid
insoluble binder.
U.S. Patent Nos. 4,200,487 and 4,242,404 to Bodoc et al. describe glass inats
that
include individual glass filaments and extended glass fiber elements. The
extended glass
fiber elements are formed from bundles of glass fibers that slide apart and
become
connected longitudinally when the slurry is agitated. It is asserted that the
glass fiber
elements contribute to high strength properties of the mat and that the
individual filaments
provide a uniform denseness necessary for the impregnation of asphalt in the
manufacturing of roofing shingles. The mats are formed by a wet-laid process.
U.S. Patent No. 6,767,851 and U.S. Patent Application Publication No.
2002/0092634 to Rokman et al. disclose non-woven mats in which at least 20% of
the
fibers are present as fiber bundles having about 5 - 450 fibers per bundle. In
preferred
embodiments, at least 85% of the fibers in the mats are in the form of
bundles. The fibers
are held in the bundles by a substantially non-water soluble sizing such as an
epoxy resin
or PVOH. The bundles may comprise at least 10% reinforcing fibers such as
glass fibers.
The mat may be made by a foam or water process.
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Despite the existence of these dried chopped glass bundles and fiber bundle-
containing mats, there remains a need in the art for a cost-effective and
efficient process
for increasing the glass fiber content resulting from the use of wet-laid
glass mats.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide chopped glass fiber
bundles that
may be used as a replacement for conventional glass forms utilized in mat
fonning
applications. The chopped glass fiber bundles are fonned of a plurality of
individual glass
fibers positioned in a substantially parallel orientation to each other. The
glass fibers used
to form the chopped fiber bundles may be any type of glass fiber. Although
reinforcing
fibers such as natural fibers, mineral fibers, carbon fibers, ceramic fibers,
and/or synthetic
fibers may be present in the chopped glass fiber bundles, it is preferred that
all of the fibers
in the chopped glass fiber bundles are glass fibers. The fibers are at least
partially coated
with a size composition that includes one or more film forming agents (such as
a
polyuretha-ne film former, a polyester film forlner, and/or an epoxy resin
film former), at
least one lubricant, and at least one silane coupling agent (such as an
aminosilane or
methacryloxy silane coupling agent). The size on the glass fibers maintains
bundle
integrity during the formation and subsequent processing of the glass fiber
bundles and
assists in filamentizing the chopped glass fiber bundles during subsequent
processing steps
in order to form a mat that gives an aesthetically pleasing look to the
finished product.
It is also an object of the present invention to provide a method of forming
cliopped
glass fiber bundles that may be used as a replacement for conventional glass
forms utilized
in mat forming applications. A size composition including one or more film
forming
agents (such as a polyurethane film former, a polyester film former, and/or an
epoxy resin
film former), at least one lubricant, and at least one silane coupling agent
(such as an
aminosilane or methacryloxy silane coupling agent) is applied to attenuated
glass fibers in
a conventional manner. The sized glass fibers may be split into glass fiber
strands
containing a predetermined number of individual glass fibers. It is desirable
that the glass
fiber bundles have a bundle tex of 20 - 200 g/km. The glass fiber strands may
then be
chopped into wet chopped glass fiber bundles and dried to consolidate or
solidify the
sizing coinposition. Preferably, the wet bundles of fibers are dried in an
oven such as a
conventional dielectric (RF) oven, a fluidized bed oven such as a Cratec oven
(available
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from Owens Corning), or a rotary tray thermal oven to form the chopped glass
fiber
bundles.
It is also an object of the present invention to provide a method of forming
chopped
glass fiber bundles that utilizes a heat transfer chamber to adiabatically dry
the wet, sized
glass fibers. A size composition including one or more film forming agents
(such as a
polyurethane film former, a polyester film former, and/or an epoxy resin film
former), at
least one lubricant, and at least one silane coupling agent (such as an
aminosilane or
methacryloxy silane coupling agent) is applied to glass fibers attenuated by a
bushing. The
sized glass fibers may then be passed through a heat transfer chamber where
air heated by
the bushing is drawn into said heat transfer chamber to substantially dry the
sizing on the
glass fibers. The dried glass fibers exiting the heat transfer chamber may be
split into glass
fiber strands that contain a preselected number of individual glass fibers. It
is desirable
that the glass fiber bundles have a bundle tex of 20 - 200 g/kn. The glass
strands may be
gathered together into a single tow prior to chopping the glass strands into
chopped glass
fiber bundles. In one exemplary embodiment, the chopped fiber buildles are
further dried
in a conventional dielectric (RF) oven, a fluidized bed oven such as a Cratec
oven
(available from Owens Corning), or a rotary tray thermal oven.
It is an advantage of the present invention that the chopped glass fiber
bundles may
be formed at a faster rate of speed than conventional air-laid processes.
Increasing the rate
of speed that the chopped glass fiber bundles can be produced permits for a
higher
throughput and additional product that can be sold to the customers.
It is another advantage of the present invention that the chopped glass fiber
bundles
can be formed with low manufacturing costs since the wet glass fibers do not
have to be
dried and chopped in separate steps.
It is yet another advantage of the present invention that the wet fibers
utilized to
form the chopped glass fiber bundles produce little or no fuzz in the final
chopped strand
mat.
The foregoing and other objects, features, and advantages of the invention
will
appear more fiilly hereinafter from a consideration of the detailed
description that follows.
It is to be expressly understood, however, that the drawings are for
illustrative purposes
and are not to be construed as defining the limits of the invention.
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BRIEF DESCRIPTION OF THE DRA.WINGS
The advantages of this invention will be apparent upon consideration of the
following detailed disclosure of the invention, especially when taken in
conjunction with
the accompanying drawings wherein:
FIG. 1 is a schematic illustration of a chopped straiid bundle according to an
exemplary embodiment of the present invention;
FIG. 2 is a flow diagram illustrating steps of an exemplary process for
forming
glass fiber bundles according to at least one embodiment of the present
invention;
FIG. 3 is a schematic illustration of a processing ling for forming dried
chopped
strand bundles according to one exemplary embodiment of the present invention;
FIG. 4 is a schematic illustration of a processing line for forming dried
chopped
strand bundles according to at least one other exemplary embodiment of the
invention;
FIG. 5 is a schematic illustration of a processing line for forming a chopped
strand
mat utilizing chopped strand bundles according to the present invention;
FIG. 6 is a graphical illustration of the laminate tensile strengths in the
machine
direction and the cross direction for conventional chopped strand mats and
chopped strand
mats utilizing dried chopped glass fiber bundles according to the instant
invention;
FIG. 7 is a graphical illustration of the laminate tensile moduli in the
machine
direction and the cross direction for conventional chopped strand mats and
chopped strand
mats utilizing dried chopped glass fiber bundles according to the instant
invention;
FIG. 8 is a graphical illustration of the laminate flexural strengtlis in the
machine
direction and the cross direction for conventional chopped strand mats and
chopped strand
mats utilizing dried chopped glass fiber bundles according to the instant
invention;
FIG. 9 is a graphical illustration of the laminate flexural moduli in the
machine
direction and the cross direction for conventional chopped strand mats and
chopped strand
mats utilizing dried chopped glass fiber bundles according to the instant
invention;
FIG. 10 is a graphical illustration of the tensile strength in the machine
direction
for laminates formed utilizing dried chopped glass fiber bundles according to
the present
invention;
FIG. 11 is a graphical illustration of the tensile strength in the cross-
machine
direction for laminates formed utilizing dried chopped glass fiber bundles
according to the
present invention;
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FIG. 12 is a graphical illustration of IZOD notched impact strength of bulk
molding compounds made with glass fibers sized with sizing compositions
according to
the present invention versus control at 0 degrees;
FIG. 13 is a graphical illustration of IZOD notched impact strength of bulk
molding compounds made with glass fibers sized with sizing compositions
according to
the present invention versus control at 90 degrees.
DETAILED DESCRIPTION AND
PREFERRED EMBODIMENTS OF THE INVENTION
Unless defined otherwise, all technical and scientific terms used herein have
the
same meaning as commonly understood by one of ordinary skill in the art to
which the
invention belongs. Although any methods and materials similar or equivalent to
those
described herein can be used in the practice or testing of the present
invention, the
preferred methods and materials are described herein.
In the drawings, the thickness of the lines, layers, and regions may be
exaggerated
for clarity. It is to be noted that like numbers found throughout the figures
denote like
elements. The terms "top", "bottom", "side", "upper", "lower" and the like are
used
herein for the purpose of explanation only. It will be understood that when an
element is
referred to as being "on," another element, it can be directly on or against
the other
element or intervening elements may be present. The terms "sizing", "size",
"sizing
composition", and "size composition" may be interchangeably used herein. The
terms
"strand" and "bundle" may also be used interchangeably herein.
The present invention relates to chopped glass fiber bundles that may be used
as a
replacement for conventional glass forms utilized in mat forming applications
and to a
process for forming such chopped glass fiber bundles. An example of a chopped
glass
fiber bundle according to the present invention is depicted generally in FIG.
1. As shown
in FIG. 1, the cllopped glass fiber bundle 10 is formed of a plurality of
individual glass
fiber 12 having a diameter 16 and a length 14. The individual glass fibers 12
are
positioned in a substantially parallel orientation to each other in a tight
knit or "bundled"
fornnation. As used herein, the phrase "substantially parallel" is meant to
denote that the
individual glass fibers 12 are parallel or nearly parallel to each other. The
chopped glass
fiber bundles according to the present invention may be used in the formation
of chopped
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strand mats (CSM), in forming sheet molding compounds (SMC), in bulk molding
compounds (BMC), in hand lay-up applications, and in spray-up applications. In
addition,
the chopped glass fiber bundles may be used to create preforms for use in
resin transfer
molding (RTM) or structural reaction injection molding (SRIM). In structural
reaction
injection molding, the dried chopped glass fiber bundles 10 are blown onto a
screen to take
the shape of the desired part, sucli as a truck bed or automobile door inner.
The glass fibers used to form the chopped fiber bundles may be any type of
glass
fiber, such as A-type glass fibers, C-type glass fibers, E-type glass fibers,
S-type glass
fibers, ECR-type glass fibers (for exatraple, Advantex glass fibers
commercially available
from Owens Corning), wool glass fibers, or combinations thereof. In at least
one preferred
embodiment, the glass fibers are wet use chopped strand glass fibers (WUCS).
Wet use
chopped strand glass fibers may be formed by conventional processes known in
the art. It
is desirable that the wet use chopped strand glass fibers have a moisture
content of from
about 5 to about 30%, and even more desirably a moisture content of from about
5 to about
15%.
The use of other reinforcing fibers such as natural fibers, mineral fibers,
carbon
fibers, ceramic fibers, and/or synthetic fibers such as polyester,
polyethylene, polyethylene
terephthalate, polypropylene, and/or polyparaphenylene terephthalamide (sold
commercially as Kevlar ) in the bundles of fibers 10 is considered to be
within the
purview of the invention. As used herein, the term "natural fiber" is meant to
indicate
plant fibers extracted from any part of a plant, including, but not limited
to, the stem,
seeds, leaves, roots, or bast. The inclusion of synthetic fibers in the fiber
bundles gives a
mat formed from the fiber bundles more flexibility or conformability to small
radii.
Further, the use of synthetic fibers may act as a mat binder in later
processing to hold the
chopped glass fiber bundles 10 together and form a chopped strand mat.
However, it is
preferred that all of the fibers in the bundles 10 are glass fibers.
In one exemplary embodiment, shown generally in FIG. 2, the process of forming
the chopped glass fiber bundles 10 includes forming glass fibers (Step 20),
applying a size
composition to glass fibers (Step 22), splitting the fibers to obtain a
desired bundle tex
(Step 24), chopping wet fiber strands to a discrete length (Step 26), and
drying the wet
strands (Step 28) to form the chopped glass fiber bundles.
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As shown in more detail in FIG. 3, glass fibers 12 may be formed by
attenuating
streams of a molten glass material (not shown) from a bushing or orifice 30.
The
attenuated glass fibers 12 may have diameters of about 8 to about 23 microns,
preferably
from 10 - 16 microns. After the glass fibers 12 are drawn from the bushing 30,
an aqueous
sizing composition is applied to the fibers 12. The sizing may be applied by
conventional
methods such as by the application roller 32 shown in FIG. 3 or by spraying
the size
directly onto the fibers (not shown). The size protects the glass fibers 12
from breakage
during subsequent processing, helps to retard interfilainent abrasion, and
ensures the
integrity of the strands of glass fibers, for exatnple, the interconnection of
the glass
filaments that forrn the strand.
In the present invention, the size on the glass fibers 12 also maintains
bundle
integrity during the formation and subsequent processing of the glass fiber
bundles 10,
such as in a wet-laid process to form a chopped strand mat (CSM). In this
process, the
glass fiber bu.ndles 10 are added to a white water slurry aiid agitated. The
slurry is then
deposited onto a moving screen where a majority of the water is removed to
form a web, a
binder is applied, and the web is dried to remove the remaining water and cure
the binder.
Unlike conventional glass bundles, chopped glass fiber bundles 10 sized with
the size
composition described below remain in a bundle forln or substantially in a
bundle forni in
the white water slurry during the formation of the chopped strand mat. In at
least one
exemplary embodiment, the fibers 12 within the bundles 10 maybe sized with the
sizing
composition so that a predetermined amount of fibers 12 disperse from the
fiber bundles
10 in the slurry during agitation. The size composition on the glass fibers 12
also assists in
filamentizing the bundles 10 during subsequent processing steps in order to
form a mat
that gives an aesthetically pleasing look to the finished product.
Another example of where the size on the glass fibers maintains bundle
integrity
during processing is in molding a sheet molding compound (SMC). In molding a
sheet
molding compound, a matched metal die is loaded (filled) with a sheet molding
compound
or bulk molding compound (BMC). It is desirable that the glass fiber bundles
10 have
bundle integrity when the metal die closes and is heated so that the sheet
molding
compound (or BMC) can flow and fill the die to form the desired part. However,
if the
glass fiber bundles 10 disassociate into single fibers within the die before
the flow is
complete, the individual glass fibers form clumps and incompletely fill the
die, thereby
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resulting in a defective part. On the other hand, after the sheet or bulk
molding compound
has flowed and the die has been filled, it is desirable that the glass fiber
bundles 10
filamentize at that time to reduce the occurrence of or even prevent
"telegraphing" or
"fiber print", which is the outline of the glass fiber bundles 10 at the part
surface. Thus,
the size on the glass fibers 12 also assists in filamentizing the chopped
glass fiber bundles
during future processing steps (such as molding a chopped strand mat formed of
the
glass fiber bundles 10) to form an aesthetically pleasing final product.
The size composition applied to the glass fibers 12 includes one or more film
forming agents (such as a polyLirethane film former, a polyester film former,
and/or an
10 epoxy resin film former), at least one lubricant, and at least one silane
coupling agent (such
as an aminosilane or methacryloxy silane coupling agent). When needed, a weak
acid such
as acetic acid, boric acid, metaboric acid, succinic acid, citric acid, formic
acid, and/or
polyacrylic acids may be added to the size composition to assist in the
hydrolysis of the
silane coupling agent. The size composition may be applied to the glass fibers
12 with a
Loss on Ignition (LOI) of from about 0.05 to about 2.0% on the dried fiber.
LOI may be
defined as the percentage of organic solid matter deposited on the glass fiber
surfaces.
Film formers are agents which create improved adhesion between the glass
fibers
12, which results in improved strand integrity. Suitable film formers for use
in the present
invention include polyurethane film formers, epoxy resin film formers, and
unsaturated
polyester resin film formers. Specific examples of film formers include, but
are not
limited to, polyurethane dispersions such as Neoxil 6158 (available from DSM);
polyester
dispersions such as Neoxil 2106 (available from DSM), Neoxil 9540 (available
from
DSM), and Neoxil PS 4759 (available from DSM); and epoxy resin dispersions
such as
PE-412 (available from AOC), NX 9620 (available from DSM), Neoxil 0151
(available
from DSM), Neoxi12762 (DSM), NX 1143 (available from DSM), AD 502 (available
from AOC), Epi Rez 5520 (available from Hexion), Epi Rez 3952 (available from
Hexion), Witcobond W-290 H (available from Chemtura), and Witcobond W-296
(available from Chemtura). The film former(s) may be present in the size
coniposition
from about 5 to about 95% by weight of the active solids of the size,
preferably from about
40 to about 80% by weight of the active solids.
The size composition also includes one or more silane coupling agents. Silane
coupling agents enhance the adhesion of the film forming agent(s) to the glass
fibers 12
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and to reduce the level of fuzz, or broken fiber filaments, during subsequent
processing.
Examples of silane coupling agents which may be used in the present size
composition
may be characterized by the functional groups amino, epoxy, vinyl,
methacryloxy, ureido,
isocyanato, and azamido. Suitable coupling agents for use in the size
composition are
available commercially, such as, for example, y-aminopropyltriethoxysilane (A-
1100
available from General Electric) a7,id methacryloxypropyltriethoxysilane (A-
174 available
from General Electric). The silane coupling agent may be present in the size
composition
in an amount of from about 5 to about 30% by weight of the active solids in
the size
composition, and even more preferably, in an amount of from about 10 to about
15% by
weight of the active solids.
In additioii, the size composition may include at least one lubricant to
facilitate
manufacturing. The lubricant may be present in the size composition in an
amount of from
about 0 to about 15% by weight of the active solids in the size composition.
Preferably,
the lubricant is present in an amount of from about 5 to about 10% by weight
of the active
solids. Although any suitable lubricant may be used, specific examples of
lubricants
suitable for use in the size composition include stearic ethanolamide, sold
under the trade
designation Lubesize K-12 (available from AOC); PEG 400 MO, a monooleate ester
having about 400 ethylene oxide groups (available from Cognis); and Emery 6760
L, a
polyethyleneimine polyamide salt (available from Cognis).
It has been discovered that certain families of chemistry in combination are
especially effective in causing the chopped glass fiber bundles 10 to remain
in a bundle
form during subsequent processing. For example, urethane-based film forming
dispersions
in combination with aminosilanes, such as, for example, y-
aminopropyltriethoxysilane
(sold as A-1100 by General Electric) are effective in the size composition to
keep the
individual glass fibers 12 bundled together. Adding an additive such as a
polyurethane-
acrylic alloy to the urethane-based sizing composition has also been found to
help maintain
bundle integrity.
Additionally, epoxy-based film former dispersions in combination with
epoxy curatives are effective sizing compositions for use in the present
invention. In
particular, an epoxy-based film former such as Epi-Rez 5520 and an epoxy
curative such
as DPC-6870 available from Resolution Performance Products fonns an effective
sizing
composition, particularly in combination with a methacryloxy silane such as
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methacryloxypropyltriethoxysilane (commercially available as A- 174 from
General
Electric).
Further, unsaturated polyester resin film formers have been found to be
effective in
forming a useful sizing composition. For example, an unsaturated polyester
resin film
former such as PE-412 (an unsaturated polyester in styrene that has been
emulsified in
water (AOC)) or Neoxil PS 4759 (available from DSM) are effective sizes for
use in the
present invention. Unsaturated polyester film formers may be used alone or in
combination with a benzoyl peroxide curing catalyst such as Benox L-40LV
(Norac
Company, Inc.). The benzoyl peroxide curing catalyst catalyzes the cure
(crosslinking) of
the unsaturated polyester resin and renders the film surrounding the glass
fibers water
resistant.
The sizing composition may optionally contain conventional additives including
antifoaming agents such as Drew L-139 (available from Drew Industries, a
division of
Ashland Chemical), antistatic agents such as Emerstat 6660A (available from
Cognis),
surfactants such as Surfyno1465 (available from Air Products), Triton X- 100
(available
from Cognis), and/or thickening agents. Additives may be present in the size
composition
from trace amounts (such as < about 0.1 % by weight of the active solids) up
to about 5%
by weight of the active solids.
After the glass fibers 12 are treated with the sizing composition, they are
gathered
and split into fiber strands 36 having a specific, desired number of
individual glass fibers
12. The splitter shoe 34 splits the attenuated, sized glass fibers into fiber
strands 36. The
glass fiber strands 36 may be passed through a second splitter shoe (not
shown) prior to
chopping the fiber strands 36. The specific number of individual glass fibers
12 present in
the fiber strands 36 (and therefore the number of splits of the glass fibers
12) will vary
depending on the particular application for the chopped glass fiber bundles
10. For
example, assuming that a bushing has 4000 orifices for attenuating glass
fibers, it would
be necessary to split the attenuated glass fibers 40 ways to achieve a bundle
of glass fibers
that contain 100 fibers. The bundle tex of that particular bundle of glass
fibers depends on
the diameter of the glass fibers forming the bundle. In the example given
above where the
fiber bundles contain 100 individual glass fibers, if the fiber diameter of
the glass fibers is
12 microns, the calculated bundle tex is 29. If the fiber diameter is 16
microns, the
calculated bundle tex is 51 g/km. It is desirable that the glass fibers 12 are
split into
12
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bundles of fibers that have a specific number of individual fibers to achieve
a bundle tex of
about 20 to about 200 g/km, preferably from about 30 to about 50 g/km.
The fiber strands 36 are passed from the gathering shoe 38 to a chopper 40/cot
60
combination where they are chopped into wet chopped glass fiber bundles 42
having a
lengtli of approximately about 0.125 to about 3 inches, and preferably about
0.25 to about
1.25 inches. The wet, chopped glass fiber bundles 42 may fall onto a conveyor
44 (such as
a foraminous conveyor) for conveyance to a drying oven 46. Alternatively, the
wet
bundles of chopped glass fibers 42 may be collected in a container (not
illustrated) for use
at a later time.
The bundles of wet, sized chopped fibers 42 are then dried to consolidate or
solidify the sizing composition. Preferably, the wet bundles of fibers 42 are
dried in an
oven 46 such as a conventional dielectric (RF) oven, a fluidized bed oven such
as a
Cratec oven (available from Owens Corning), or a rotary tray thermal oven to
form the
chopped glass fiber bundles 10. The dried chopped glass fiber bundles 10 may
then be
collected in a collection container 48. In exemplary embodiments, greater than
(or equal
to) about 99% of the free water (t1zat is, water that is external to the
chopped fiber bundles
42) is removed. It is desirable, liowever, that substantially all of the water
is removed by
the diying oven 46. It should be noted that the phrase "substantially all of
the water" as it
is used herein is meant to denote that all or nearly all of the free water
from the fiber
bundles 42 is removed.
In at least one exemplary embodiment, the wet bundles of glass fibers 42 are
dried
in a conventional dielectric (RF) oven. The dielectric oven includes spaced
electrodes that
produce alternating high-frequency electrical fields between successive
oppositely charged
electrodes. The wet bundles of glass fibers 42 pass between the electrodes and
through the
electrical fields where the high alternating frequency electrical fields act
to excite the water
molecules and raise their molecular energy to a level sufficient to cause the
water within
the wet chopped fiber bundles 42 to evaporate.
Dielectrically drying the bundles of wet glass fibers 42 enhances fiber-to-
fiber
cohesion and reduces bundle-to-bundle adhesion. The dielectric energy
penetrates the wet
bundles of chopped glass fibers 42 evenly and causes the water to quickly
evaporate,
helping to keep the wet glass bundles 42 separated from each other.
Additionally, the
dielectric oven permits the wet glass fiber bundles 42 to be dried with no
active method of
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fiber agitation as is conventionally required to remove moisture from wet
fibers. This lack
of agitation reduces or eliminates the attrition or abrasion of fibers as is
commonly seen in
conventional fluidized bed and tray drying ovens due to the high air flow
velocities within
the ovens and the mechanical motion of the fibrous material in the beds. In
addition, the
lack of agitation greatly increases the ability of the dielectric oven to
maintain the glass
fibers in bundles and not filamentize the glass fiber strands as in aggressive
conventional
thermal processes.
In alternative embodiments, the wet chopped glass fiber bundles 42 may be
dried in
a fluidized bed oven such as a Cratec oven or in a rotating tray oven. In
both the Cratec
drying oven and rotating try oven, the wet chopped glass fiber bundles 42 are
dried and the
sizing composition on the fibers is solidified using a hot air flow having a
controlled
temperature. The dried fiber bundles 10 may then passed over screens to remove
longs,
fuzz balls, and other undesirable matter before the chopped glass fiber
bLmdles 10 are
collected. In addition, the high oven temperatures that are typically found in
Cratec and
rotating tray ovens allow the size to quickly cure to a very higll level of
cure which reduces
occurrences of premature filamentization.
In a second embodiment of the present invention depicted generally in FIG. 4,
glass
fibers 12 are attenuated from a bushing 30. An aqueous sizing composition as
described in
detail above is applied to the attenuated glass fibers 12 to form wet sized
glass fibers 50.
The sizing may be applied by conventional methods such as by an external
application
roller 32 or by spraying the size directly onto the glass fibers 12 (not
shown). It is
considered to be within the purview of the invention to position a size
applicator internally
within the heat transfer chamber 52. The wet sized glass fibers 50 then enter
the heat
transfer chamber 52 and ambient air is drawn into the uppermost end 54 of the
heat
transfer chamber 52 from circumferentially around the bushing 30.
As shown in FIG. 4, the heat transfer chamber 52 extends beneath the size
applicator 32 and is positioned with the uppermost end 54 of the heat transfer
chamber 52
in a sufficiently close proximity to the bushing 30 so that the air being
drawn into the
uppermost end 54 of the heat transfer chamber 52 is heated by the extreme heat
generated
by the bushing 30. In addition, the heat transfer chamber 52 is essentially
circumferentially disposed about the sized glass fibers 50 so that the heated
air may
evaporate any water or solvent present in the size composition on the wet
glass fibers 50.
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The heat transfer chainber 52 extends downwardly from the size applicator 32 a
distance
that is sufficient to dry or substantially dry the wet sized glass fibers 50.
In a preferred
embodiment, the moisture content of the glass fibers 50 is less than about
0.05%. The wet
glass fibers 50 travel througli the heat transfer chamber 52 and exit the
chamber 52 as
dried glass fibers 56. Such an adiabatic process is described in detail in
U.S. Patent No.
5,055,119 to Flautt et al..
The dried sized glass fibers 56 are then gathered and split into dried fiber
strands
58 having a specific, desired number of individual glass fibers 12. A splitter
shoe 34 splits
the dried sized glass fibers 56 into dried fiber strands 58, which may then be
gathered by a
gathering shoe 38 into a single tow 59 for chopping. It is to be appreciated
that the splitter
shoe 34 may be positioned internally (not illustrated) in the heat transfer
chamber 52 to
split the wet glass fibers 50 into fiber strands prior to exiting the heat
transfer chamber 52.
In this, situation, the gathering shoe 38 may or may not be positioned within
the heat
transfer chamber 52. It is also to be appreciated that the splitter shoe 34
may be positioned
between the size applicator 32 and the heat transfer chamber 52 to split the
glass fibers 12
prior to entering the heat transfer chamber 52 (not shown).
The tow of combined glass fiber strands 59 may be chopped by a conventional
cot
60 and cutter 40 combination to form the dried chopped fiber bundles 10. As
described
above, the dried chopped fiber bundles 10 may have a length of about 0.125 to
about 3
inches, and preferably a length of about 0.25 to about 1.25 inches. In at
least one preferred
embodiment, the dried sized glass fibers 56 are split into dried bundles of
fibers 58 with a
bundle tex of from about 20 to about 200 g/kn, and preferably from about 30 to
about 50
g/km. The dried, chopped glass fiber bundles 10 may fall onto a collection
container 48
for storage or placed onto a conveyor for an in-line formation of a chopped
strand mat
(embodiment is not illustrated). In an alternate embodiment, the dried,
chopped fiber
bundles 10 may be placed onto a conveyor (not shown) for conveyance to a
conventional
dielectric (RF) oven, a fluidized bed oven such as a Cratec oven (available
from Owens
Coming), or a rotary tray thermal oven to fiirther dry them.
In use, the dried chopped glass fiber bundles 10 may be used to form a chopped
strand mat 84, as shown in FIG. 5. The dried chopped glass bundles 10 may be
provided
to a conveyor 62 by a storage container 60. The dried chopped glass fiber
bundles 10 are
placed into a mixing tank 64 that contains various surfactants, viscosity
modifiers,
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defoaming agents, and/or other chemical agents with agitation to form a
chopped glass
fiber bundle slurry (not shown). The slurry may be passed through a machine
chest 66 and
a constant level chest 68 to further disperse any fibers selectively released
from the
chopped glass fiber bundles 10 by the size composition. The glass fiber bundle
slurry may
then be transferred from the constant level chest 68 to a head box 70 where
the slurry is
deposited onto a moving screen or foraminous conveyor 74 and a substantial
portion of the
water fiom the sluny is removed to form a web 72. The water may be removed
from the
web 72 by a conventional vacuum or air suction system (not illustrated in FIG.
5). A
binder 76 is then applied to the web 72 by a binder applicator 78. The binder-
coated web
80 is then passed through a drying oven 82 to remove any remaining water and
cure the
binder. The formed non-woven chopped strand mat 84 that emerges from the oven
82
includes randomly dispersed glass fiber bundles. The non-woven chopped strand
mat 84
may be rolled onto a take-up roll 86 for storage for later use.
The binder may be an acrylic binder, a styrene acrylonitrile binder, a styrene
butadiene rubber binder, a urea formaldehyde binder, or mixtures thereof.
Preferably, the
binder is a standard thermosetting acrylic binder formed of polyacrylic acid
and at least
one polyol (for exasnple, triethanolamine or glycerine). Examples of suitable
acrylic
binders for use in the present invention include a plasticized
polyvinylacetate binder such
as Vinamul 8831 (available from Celenese) and modified polyvinylacetates such
as
Duracet 637 and Duracet 675 (available from Franklin International). The
binder may
optionally contain conventional additives for the improvement of process and
product
performance such as dyes, oils, fillers, colorants, UV stabilizers, coupling
agents (for
exarnple, aminosilanes), lubricants, wetting agents, surfactants, and/or
antistatic agents.
There are numerous advantages provided by the chopped glass fiber bundles 10
of
the present invention. For instance, the chopped glass fiber bundles 10 may be
formed at a
significantly fast rate, especially when compared glass bundles formed by
conventional
air-laid processes. Increasing the rate of speed that the chopped glass fiber
bundles can be
produced permits for a higher throughput and additional product that can be
sold to the
customers. In addition, the chopped glass fiber bundles can be formed with low
manufacturing costs since the fibers do not have to be dried and chopped in
separate steps.
In addition, the chopped glass fiber bundles 10, when utilized in the
formation of
chopped strand mats in the wet process described above, provides for a mat
that has a
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substantially uniform distribution of glass (aerial density) and is white in
appearance. It is
also advantageous that the wet fibers utilized to form the chopped glass fiber
bundles
produce little or no fuzz in the final chopped strand mat.
Having generally described this invention, a further understanding can be
obtained
by reference to certain specific examples illustrated below which are provided
for purposes
of illustration only and are not intended to be all inclusive or limiting
ttnless otherwise
specified.
Examples
Example 1: Formation of Dry Chopped Glass Fiber Bundles
The sizing formulations set forth in Tables 1- 4 were prepared in buckets as
described generally below. To prepare the size compositions, approximately 90%
of the
water and, if present in the size composition, the acid(s) were added to a
bucket. The
silane coupling agent was added to the bucket and the mixture was agitated for
a period of
time to permit the silane to hydrolyze. After the hydrolyzation of the silane,
the lubricant
and fihn former were added to the mixture with agitation to form the size
coinposition.
The size composition was then diluted with the remaining water to achieve the
target mix
solids of approximately 4.5% mix solids.
TABLE 1
Polyurethane Size Composition A
Component of Size % by Weight of
Composition Active Solids
W290H (a 83.64
A-187(b) 1.12
A-1100( 4.68
A-100 7 9.95
Lubesize K-12(e) 0.06
(a) polyurethane film forming dispersion (Cognis)
(') epoxy curative (Resolution Performance Products)
( )y-aminopropyltriethoxysilane (General Electric)
(d) polyurethane-acrylic alloy (Cognis)
(e) stearic ethanolamide (AOC)
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TA.BLE 2
Polyurethane Size Composition B
Component of Size % by Weight of
Composition Active Solids
W296 (a 491.76
A-187 "31 6.79
A-1100( 25.86
PEG 400 MO (d) 2.21
(a) polyurethane film forming dispersion (Chemtura)
(b) epoxy curative (Resolution Performance Products)
(,-)y-aminopropyltriethoxysilane (General Electric)
(d) polyurethane-acrylic alloy (Cognis)
(e) monooleate ester (Cognis)
TABLE 3
Epoxy Size Coin osition A
Component of Size % by Weight of
Composition Active Solids
ER 5520(a) 46.15
DPC-6870(b 46.15
PEG 400 MO( ) 3.08
A-174(d) 4.62
epoxy resin film forming dispersion in water (Resolution Performance
Products)
(b) epoxy curative (Resolution Performance Products)
(0monooleate ester (Cognis)
(d) methacryloxypropyltrimethoxysilane (General Electric)
TABLE 4
Epoxy Size Composition D
Component of Size % by Weight of
Composition Active Solids
ER 3546(a) 47.20
DPC-6870(b, 47.20
PEG 400 MO( ) 0.88
A-174td~
1 4.72
ta) epoxy resin film forming dispersion (Resolution Performance Products)
(b) epoxy curative (Resolution Performance Products)
(0monooleate ester (Cognis)
(d) methacryloxypropyltrimethoxysilane (General Electric)
Each of the sizes were applied to E-glass in a conventional manner (such as a
roll-
type applicator as described above. The E-glass was attenuated to 13 m glass
filaments
in a 75 lb/hr throughput bushing fitted with 2052 hole tip plate. The
filaments were
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gathered and split 16 ways to achieve 128 filaments per glass fiber bundle and
a bundle tex
of about 43 g/km. The glass fiber bundles were then chopped with a mechanical
cot -
cutter combination to a length of approximately 1 1/4 inches and gathered into
a plastic
pan. The chopped glass fibers contained approximately 15% forming moisture.
This
moisture in chopped glass fiber bundles was removed in a dielectric oven (40
MHz, Radio
Frequency Co.) to form dried chopped glass fiber bundles.
Example 2: Formation of Chopped Strand Mat UsiniZ Dried Chopped Glass
Fiber Bundles
The dried chopped fiber bundles formed in accordance with the procedures set
forth in Example 1 were used to form four chopped glass mats. The dried
chopped fiber
bundles (each containing a different size composition set forth in Tables 1-
4) were
suspended in 250 gallon mixing tanks in wliich the appropriate additives
(surfactants,
dispersants, and the like) were added with agitation to form chopped glass
fiber bundle
slurry slurries. The components of the white water slurry (other than water)
are set forth in
Table 5.
TABLE 5
White Water Amount
Components (ppm)
Drewfloc 270(a) 400 - 900
Surfynol 465(b 50 - 200
Drew L-139~ ) 5 - 25
Nalco 7330(d) 1-5
anionic polyacrylamide (available from Drew Industries)
(') nonionic surfactant (available from Air Products)
( ) antifoaming agent (available from Drew Industries)
(d) biocide (ONDEO Nalco)
The glass slurries were each deposited onto a moving chain where a majority of
the
water was removed by a vacuuin to form a web. A plasticized polyvinylacetate
mat binder
was applied to the glass webs (Vinamul 8831 from Celenese) by a weir (curtain
coater).
The webs were then passed through a forced air oven at 450 F for 30 seconds to
remove
the remaining water from the webs, cure the binder, and form the chopped glass
mats. The
basis weight of the mats were determined to be approximately 1 az/ft 2. It was
also
determined that the binder was present on the mats at 5.0% by weight. The mats
were
extremely white and visually showed excellent aerial density. In addition, the
chopped
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glass mats displayed dry tensile strengths of 30 lb in the machine direction
(MD) and 25 lb
in the cross-machine direction (CD).
Laminates were prepared from the chopped glass mats with a polyester resin
(AOC
R937) and catalyzed with Attofina DDM9 catalyst (2-Butanone Peroxide). To
facilitate
comparison, the laminates containing the inventive chopped glass fiber bundles
all had a 3
oz/ft2 basis weight and substantially equivalent thicknesses. Simulating hand
layup, the
laminates were formed in a hydraulic press under nominal temperature (120 F)
and
pressure for about 30minutes. Pressure, at the low end of the press range was
10,000 lb for
the 14 in 2 laminates, which translates to about 50 psi. The laminates
underwent post-cure
in an oven for 2 hours at 200 F before mechanical testing.
The laminates containing the inventive chopped glass fiber bundles were tested
for
tensile strength and flexural strength. The tensile strength was detennined
according to the
testing procedures set forth in ASTM D5083 and flexural strength was
determined
according to the testing procedures set forth in ASTM D790. The comparative
mats are
set forth in Table 6.
TABLE 6
Conventional
Description
Mat
M723A 1 OZ/ft2 chopped strand mat from Owens Coming
M8643 1 oz/ftZ electrical-pultrusion grade continuous filament
mat from Owens Corning
M8610 1 oz/ft2 general purpose continuous filament mat from
Owens Coniing
Mechanical testing of the laminates containing the inventive chopped glass
fiber
bundles revealed a nearly equivalent performance of the inventive laininates
relative to a
standard chopped strand mat (M723A) and surprisingly, M8643 and M861 0,
continuous
filament mats (CFM). The results of the cornparative testing is set forth in
FIGS. 6 - 9.
Example 3: Formation of Dry Chopped Glass Fiber Bundles Utilizintz a Heat
Transfer Chamber
Each of the sizes set forth in Tables 1 - 4 were prepared and applied in a
conventional manner to E-glass attenuated to 13 m glass filaments in a 75
lb/hr
throughput bushing fitted with 2052 hole tip plate. The sized fibers were
split 16 ways to
achieve 128 filaments per glass fiber bundle and passed through a heat
transfer chamber
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where air heated by the extreme heat generated by the bushing was drawn into
the heat
transfer chamber to dry the glass fiber btindles. The dried glass fiber
bundles had a bundle
tex of about 43 g/km. The dried glass fiber bundles were gathered into one tow
and
chopped with a mechanical cot - cutter combination to a length of 1 1/4
inches. The
chopped glass fibers were gathered into a plastic pan. The glass fibers
contained 0%
forming moisture.
Example 4: Formation of Chopped Strand Mat Using Dried Chopped Glass
Fiber Bundles Formed Utilizing a Heat Transfer Chamber
The dried chopped fiber bundles formed in accordance with the procedures set
forth in Example 3 were used to form four chopped glass mats. The dried
chopped fiber
bundles (each containing a different size composition set forth in Tables 1-
4) were
suspended in 250 gallon mixing tanks in which the appropriate additives
(surfactants,
dispersants, and the like) were added with agitation to form chopped glass
fiber bundle
slurry slurries. The components of the white water slurry (other than water)
are set forth in
Table 7.
TABLE 7
Wliite Water Amount
Components (ppm)
Drewfloc 270(a) 400 - 900
Surfynol 465") 50 - 200
Drew L-139( ) 5 - 25
Nalco 7330(d) 1-5
ta~ anionic polyacrylamide (available fiom Drew Industries)
(') nonionic surfactant (available from Air Products)
( ) antifoaming agent (available from Drew Industries)
(d)biocide (ONDEO Nalco)
The glass slurries were each collected onto a moving chain where a majority of
the
water was removed by a vacuum to form a web. A plasticized polyvinylacetate
mat binder
was applied to the glass webs (Duracet 675 from Franklin International) by a
weir (curtain
coater). The webs were then passed through a forced air oven at 450 F for 30
seconds to
remove the remaining water firom the webs, cure the binder, and form the
chopped glass
mats. The basis weight of the mats were determined to be approximately I
oz/ft2. It was
also determined that the binder was present on the mats at 5.0% by weight. On
visual
observation, it was noted that the mats were extremely white and visually
showed
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excellent aerial density. In addition, the chopped glass mats displayed dry
tensile strengths
of 32 lb in the machine direction (MD)and 27 lb in the cross-machine direction
(CD).
Laminates were prepared from the cllopped glass mats with a polyester resin
(AOC
R937) and catalyzed with Attofina DDM9 catalyst (2-Butanone Peroxide). To
facilitate
comparison, the laminates containing the inventive chopped glass fiber bundles
were all 3
oz/ft2 basis weight and substantially equivalent thicknesses. Simulating hand
layup, the
laminates were formed in a hydraulic press under nominal temperature (120 F)
and
pressure for about 30minutes. Pressure, at the low end of the press range was
10,000 lb for
the 14 in2 laminates, which translates to about 50 psi. The laminates
underwent post-cure
in an oven for 2 hours at 200 F before mechanical testing. Mechanical testing
of the
laminates containing the inventive chopped glass fiber bundles revealed a
nearly
equivalent performance of the laminates relative to a standard chopped strand
mat
(M723A) and, surprisingly, M8643 and M8610, continuous filament mats (CFM)
(set
forth in Table 6).
Example 5: Tensile Strength of Laminates from Chopped Strand Mats Using
Dried Chopped Glass Fiber Bundles
Dried chopped fiber bundles formed in accordance with the procedures set forth
in
Example 3 were used to form four chopped glass mats as described above in
Example 4.
The dried chopped fiber bundles sized Polyurethane Size Composition A (Table
1) were
suspended in 250 gallon mixing tanks in a white water slurry containing the
components
set forth in Table 7. The glass slurries were each collected onto a moving
chain where a
majority of the water was removed by a vacuum to form a web. A plasticized
polyvinylacetate mat binder was applied to the glass webs (Duracet 675 or
Duracet 637
from Franklin International) by a weir (curtain coater). The webs were then
passed
through a forced air oven at 450 F for 30 seconds to remove the remaining
water from the
webs, cure the binder, and form the chopped glass mats.
Laininates were prepared from the chopped strand mats in accordance with the
procedure described above in Example 4. The various samples tested (Samples 1-
7) are
set forth in Table 8. Samples 1 and 2 contained Duracet 637 as a binder and
Samples 3
and 4 contained Duracet 675 as a binder. The laminates were tested for tensile
strength in
the machine direction (MD) and in the cross-machine direction (CD). The
results are set
forth in Tables 10 and 11. The results indicated that the laminates
demonstrated a bias in
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the machine direction. This demonstration of bias is contrary to mats made in
accordance
with conventional air-laid processes, which show no or virtually no bias. A
bias in the
machine direction is an advantage to the laminates because the chopped strand
mat will be
naturally stronger in the direction that a customer will pull it off of the
roll. As a result,
larger rolls may be manufactured. In addition, the additional strength would
enable a
customer to pull the chopped strand mat off the roll at a faster rate of speed
with a less
likelihood that the mat would tear. The data also demonstrates superior
strength for
laminates formed with the chopped glass fiber bundles sized with Size
Composition A
compared to the controls.
TABLE 8
Sample Description of
Cho ed Strand Mat
1 6 lys of 0.5 oz/ft2
2 2 plys of 1.5 oz/ft2
3 6 plys_of 0.5 oz/ft2
4 2 plys of 1.5 oz/ftZ
5 M723A (3 plys of 1 oz/ft ) control
6 M723A-2 (6 plys of 0.5 oz/ft2) control
7 M723A-3 (2 plys of 1.5 oz/ftz) control
Example 6: Formation of Bulk Molding Compound Utilizing Various Sizing
Compositions
One quarter inch (1/4") chopped glass fiber samples were made into bulk
molding
compounds with the formulation set forth in Table 8.
TABLE 9
Bulk Molding Compound Formulation
Component pph
(Parts Per Hundred)
Polyester Resin E-342 a) 60
Thermoplastic P-713(b 40
tBPB( l 1.5
Calwhite 11(d) 200
Zinc Stearate(e) 4
(a) unsaturated polyester resin (AOC)
thermoplastic (AOC)
tert-butylperbenzoate catalyst
(d) calcium carbonate (Cabot)
mold release agent (Aldrich Chemical Co.)
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The bulk molding compound formulation in Table 8 was prepared with various
experimental glasses sized with the various sizing compositions at 20% by
weight. The
various experimental glass fibers are set forth below as Samples 1 - 10. The
charge was
placed into a 12 inch X 18 inch tool and was molded at 10,000 psi at 265 F
for 5 minutes.
The laminates were tested for resistance to notched impact strength according
to ASTM
D256 in the 0 and 90 direction. The results are set forth in Tables 12 and
13. The
results indicated that the glass fibers sized with the experimental size
composition
demonstrated at least coinparable performance to the coiltrol. The results
were unexpected
because an at least comparable impact strength was achieved by drying the
glass fibers for
a short period of time (30 minutes) as compared to conventional processes in
which the
glass is thermally dried for at least 20 hours.
Sample 1- Polyurethane Size Composition A (Table 1) was applied to glass
fibers
and dried for 6 hours a thermal oven at 265 F.
Sample 2 - Polyurethane Size Composition A (Table 1) was applied to glass
fibers
and dried for 30 minutes in an RF oven followed by 1 hour in a thermal oven at
265 F.
Sample 3 - Polyurethane Size Composition A (Table 1) was applied to glass
fibers
and dried for 30 minutes in an RF oven followed by 2 hours at in a thermal
oven at 265 F.
Sample 4 - Polyurethane Size Composition A (Table 1) was applied to glass
fibers
and dried for 30 minutes in an RF oven followed by 2 hours in a thermal oven
at 265 F.
Sample 5 - Polyurethane Size Composition A (Table 1) was applied to glass
fibers
and dried for 30 minutes in an RF oven followed by 2 hours in a thermal oven
at 265 F.
Sample 6 - Polyurethane Size Composition A (Table 1) was applied to glass
fibers
and dried for 30 minutes in an RF oven followed by 2 hours in a thermal oven
at 265 F.
Sample 7 - Polyurethane Size Composition B (Table 2) was applied to glass
fibers
and dried for 30 minutes in an RF oven; no post heating.
Sample 8 - Epoxy Size Composition A (Table 3) was applied to glass fibers and
dried for 30 minutes in an RF oven; nG post heating.
Sample 9 - Epoxy Size Composition A (Table 3) was applied to glass fibers and
dried for 20 minutes in an RF oven; no post heating.
Sample 10 - Polyurethane Size Composition B (Table 2) was applied to glass
fibers and dried for 20 minutes in an RF oven; no post heating.
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Sample 12 - control bulk molding compound (BMC) dry use chopped strands
(101C from Rio Claro, Brazil; Owens Corning).
The invention of this application has been described above both generically
and
with regard to specific embodiments. Although the invention has been set forth
in what is
believed to be the preferred embodiments, a wide variety of alternatives known
to those of
skill in the art can be selected within the generic disclosure. The iilvention
is not
otherwise limited, except for the recitation of the claims set forth below.
