U.S. patent application number 11/691248 was filed with the patent office on 2007-10-04 for fire retardant and heat resistant yarns and fabrics treated for increased strength and liquid shedding.
This patent application is currently assigned to Chapman Thermal Products, Inc.. Invention is credited to Tyler M. Thatcher.
Application Number | 20070231573 11/691248 |
Document ID | / |
Family ID | 38255202 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070231573 |
Kind Code |
A1 |
Thatcher; Tyler M. |
October 4, 2007 |
FIRE RETARDANT AND HEAT RESISTANT YARNS AND FABRICS TREATED FOR
INCREASED STRENGTH AND LIQUID SHEDDING
Abstract
Fire retardant and heat resistant yarns and fabrics include an
inner core comprised of oxidized polyacrylonitrile encapsulated by
an outer shell comprised of a liquid-resistant and strengthening
polymer material. The liquid-resistant and strengthening polymer
material includes one or more types of cured silicone polymer
resin. A fluorchemical may be at least partially impregnated into
the inner core prior to applying the liquid-resistant and
strengthening polymer material in order to further enhance the
liquid shedding properties of the yarns or fabric. Because the
silicone polymer resin only encapsulates the yarn, but does not
form a continuous coating over the whole fabric, the treated fabric
is still able to breath through pores and spaces between individual
yarn strands that make up the fabric. The liquid-resistant and
strengthening polymer material increases the strength, abrasion
resistance, durability and liquid and gel shedding capability of
the fire retardant heat resistant yarn or fabric.
Inventors: |
Thatcher; Tyler M.; (Salt
Lake City, UT) |
Correspondence
Address: |
WORKMAN NYDEGGER;(F/K/A WORKMAN NYDEGGER & SEELEY)
60 EAST SOUTH TEMPLE, 1000 EAGLE GATE TOWER
SALT LAKE CITY
UT
84111
US
|
Assignee: |
Chapman Thermal Products,
Inc.
Salt Lake City
UT
|
Family ID: |
38255202 |
Appl. No.: |
11/691248 |
Filed: |
March 26, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60786853 |
Mar 29, 2006 |
|
|
|
Current U.S.
Class: |
428/375 |
Current CPC
Class: |
D03D 15/513 20210101;
D06M 2200/10 20130101; D06N 3/128 20130101; D06N 3/0002 20130101;
Y10T 428/2933 20150115; D06M 2200/30 20130101; D06M 15/643
20130101; D10B 2331/021 20130101; D06M 2101/28 20130101; D10B
2401/063 20130101; D10B 2503/06 20130101; D02G 3/36 20130101; D02G
3/443 20130101; D06M 15/277 20130101; D03D 1/0041 20130101 |
Class at
Publication: |
428/375 |
International
Class: |
D02G 3/00 20060101
D02G003/00 |
Claims
1. A liquid-shedding fire retardant and heat resistant yarn,
comprising: a fire retardant and heat resistant inner core
comprised of: one or more types of fire retardant and heat
resistant polymer fibers and/or filaments having an LOI of at least
about 50 and that do not burn when exposed to heat or flame having
a temperature of about 3000.degree. F.; and one or more types of
strengthening fibers and/or filaments; and an outer liquid-shedding
and strengthening shell encapsulating at least a portion of the
inner core comprised of a liquid-resistant and strengthening
polymer coating, wherein the liquid-shedding fire retardant and
heat resistant yarn has increased strength, abrasion resistance,
durability and liquid shedding ability compared to a yarn
consisting exclusively of the fire retardant and heat resistant
inner core.
2. A liquid-shedding fire retardant and heat resistant yarn as
defined in claim 1, wherein the fire retardant and heat resistant
polymer fibers and/or filaments comprise oxidized
polyacrylonitrile.
3. A liquid-shedding fire retardant and heat resistant yarn as
defined in claim 1, wherein the fire retardant and heat resistant
inner core includes oxidized polyacrylonitrile in an amount in a
range of about 25% to about 99.9% by weight of the inner core.
4. A liquid-shedding fire retardant and heat resistant yarn as
defined in claim 1, wherein the fire retardant and heat resistant
inner core includes oxidized polyacrylonitrile in an amount in a
range of about 40% to about 95% by weight of the inner core.
5. A liquid-shedding fire retardant and heat resistant yarn as
defined in claim 1, wherein the fire retardant and heat resistant
inner core includes oxidized polyacrylonitrile in an amount in a
range of about 50% to about 90% by weight of the inner core.
6. A liquid-shedding fire retardant and heat resistant yarn as
defined in claim 1, wherein the strengthening fibers and/or
filaments comprise at least one of p-aramid, m-aramid,
polybenzimidazole, polybenzoxazole,
polyphenylene-2,6-benzobisoxazole, modacrilic, polyvinyl halide,
wool, fire resistant polyester, nylon, rayon, cotton, or
melamine.
7. A liquid-shedding fire retardant and heat resistant yarn as
defined in claim 1, wherein the inner core comprises at least one
metallic strengthening filament selected from steel, stainless
steel, steel alloy, titanium, titanium alloy, aluminum, aluminum
alloy, copper, or copper alloy.
8. A liquid-shedding fire retardant and heat resistant yarn as
defined in claim 1, wherein the inner core further comprises at
least one ceramic strengthening filament selected from silicon
carbide, graphite, or a high strength ceramic that includes at
least one oxide of Al, Zr, Ti, Si, Fe, Co, Ca, Nb, Pb, Mg, Sr, Cu,
Bi, or Mn.
9. A liquid-shedding fire retardant and heat resistant yarn as
defined in claim 1, wherein the liquid-resistant and strengthening
polymer coating comprises at least one type of cured silicone
polymer resin.
10. A liquid-shedding fire retardant and heat resistant yarn as
defined in claim 1, further comprising at least one fluorochemical
at least partially impregnated within the inner core that further
imparts liquid shedding capability to the liquid-shedding fire
retardant and heat resistant yarn.
11. A liquid-shedding fire retardant and heat resistant yarn as
defined in claim 1, wherein the yarn also has flammable gel
shedding ability.
12. A liquid shedding fire retardant and heat resistant fabric
comprising: a plurality of liquid shedding fire retardant and heat
resistant yarns (according to claim 1 that have been woven,
knitted, or otherwise joined together into a fabric.
13. A liquid shedding fire retardant and heat resistant article of
manufacture formed from the liquid shedding fire retardant and heat
resistant fabric according to claim 11.
14. A liquid shedding fire retardant and heat resistant article of
manufacture as defined in claim 12, wherein the article of
manufacture is selected from the group consisting of clothing, jump
suit, glove, sock, welding bib, fire blanket, padding, protective
head gear, lining, undergarment, bedding, and drape.
15. A liquid-shedding fire retardant and heat resistant yarn,
comprising: a fire retardant and heat resistant inner core
comprised of polyacrylonitrile fibers and/or filaments; at least
one fluorochemical at least partially impregnated within the inner
core; and an outer liquid-shedding and strengthening shell
encapsulating at least a portion of the inner core comprised of a
liquid-resistant and strengthening silicone polymer coating,
wherein the liquid-shedding fire retardant and heat resistant yarn
has increased strength, abrasion resistance, durability and liquid
shedding ability compared to a yarn consisting exclusively of the
fire retardant and heat resistant inner core.
16. A liquid shedding fire retardant and heat resistant yarn as
defined in claim 15, the fire retardant and heat resistant inner
core further comprising one or more types of strengthening fibers
and/or filaments selected from the group consisting of p-aramid,
m-aramid, polybenzimidazole, polybenzoxazole,
polyphenylene-2,6-benzobisoxazole, modacrilic, polyvinyl halide,
wool, fire resistant polyester, nylon, rayon, cotton, and
melamine.
17. A liquid-shedding fire retardant and heat resistant fabric,
comprising: a plurality of liquid-shedding fire retardant and heat
resistant yarn strands woven, knitted or otherwise joined together
to form the fabric, wherein the fire retardant and heat resistant
yarn strands are comprised of polyacrylonitrile fibers and/or
filaments, wherein the fabric includes spaces between the yarn
strands; and a liquid-shedding and strengthening shell
encapsulating at least a portion of the yarn strands, wherein the
liquid-shedding and strengthening shell is comprised of a
liquid-resistant and strengthening polymer coating that is applied
so that the fabric maintains spaces between the yarn strands and
remains porous and breathable, wherein the liquid-shedding fire
retardant and heat resistant fabric has increased strength,
abrasion resistance, durability and liquid shedding ability
compared to a fabric consisting exclusively of the fire retardant
and heat resistant yarn strands.
18. A liquid shedding fire retardant and heat resistant fabric as
defined in claim 17, the fire retardant and heat resistant yarn
strands further comprising one or more types of strengthening
fibers and/or filaments selected from the group consisting of
p-aramid, m-aramid, polybenzimidazole, polybenzoxazole,
polyphenylene-2,6-benzobisoxazole, modacrilic, polyvinyl halide,
wool, fire resistant polyester, nylon, rayon, cotton, and
melamine.
19. A liquid-shedding fire retardant and heat resistant fabric as
defined in claim 17, wherein the liquid-resistant and strengthening
polymer coating comprises at least one type of cured silicone
polymer resin.
20. A liquid-shedding fire retardant and heat resistant fabric as
defined in claim 17, further comprising at least one fluorochemical
at least partially impregnated within the fire retardant and heat
resistant yarn strands that further imparts liquid shedding
capability to the liquid-shedding fire retardant and heat resistant
yarn strands.
21. A liquid shedding fire retardant and heat resistant fabric as
defined in claim 17, wherein the fabric forms at least part of an
article of manufacture selected from the group consisting of
clothing, jump suit, glove, sock, welding bib, fire blanket,
padding, protective head gear, lining, undergarment, bedding, and
drape.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit under 35 U.S.C. .sctn.
119 of U.S. provisional application Ser. No. 60/786,853, filed Mar.
29, 2006, the disclosure of which is incorporated herein in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. The Field of the Invention
[0003] The present invention is in the field of fire retardant and
heat resistant yarns and fabrics. More particularly, the present
invention is in the field of fire retardant and heat resistant
yarns comprised of oxidized polyacrylonitrile fibers and
encapsulated with a liquid-shedding and strengthening polymer, as
well as fabrics and articles of manufacture made therewith.
[0004] 2. The Relevant Technology
[0005] Fire retardant clothing is widely used to protect persons
who are exposed to fire, particularly suddenly occurring and fast
burning conflagrations. These include persons in diverse fields,
such as race car drivers, military personnel, and fire fighters,
each of which may be exposed to deadly fires and extremely
dangerous incendiary conditions. For such persons, the primary line
of defense against severe burns and even death is the protective
clothing worn over some or all of the body.
[0006] Even though fire retardant clothing presently exists, such
clothing is not always adequate to reliably offset the risk of
severe burns, or even death. This is particularly true in the case
where a person is not only exposed to flame or high heat but
splashed with a flammable hydrocarbon liquid (e.g, gasoline). This
could occur, for example, in the case of a vehicle crash or by
deliberate sabotage (e.g., a Molotov cocktail or other incendiary
device hurled at a policeman or military personnel).
[0007] A wide variety of different fibers and fibrous blends have
been used in the manufacture of fire and heat resistant fabrics.
Fire retardance, heat resistance, strength and abrasion resistance
all play an important role in the selection of materials used to
make such fabrics. However, it is difficult to satisfy all of the
foregoing desired properties. There is often a compromise between
fire retardance and heat resistance, on the one hand, and strength
and abrasion resistance, on the other.
[0008] Conventional fire retardant fabrics on the market typically
rate very high in one, or perhaps two, of the foregoing desired
properties. One example is a proprietary fabric aramid fabric sold
by DuPont, which rates high in strength and abrasion resistance at
room temperature but only provides protection against high
temperatures and flame for a relatively short period of time. When
exposed to direct flame, the leading m-aramid "fire retardant"
fabric begings to shrink and char in as little as 3 seconds, and
the degradation of the fabric increases as the duration of exposure
increases. Ironically, it is the tendency of m-aramid fabrics to
char and shrink that is purported to protect the wearer's skin from
heat and flame. M-aramid fabrics may protect the wearer from burns
for several seconds, but becomes essentially worthless as a
protective shield after it has begun to char, shrink and decompose.
Once this occurs, large holes can open up through which flame and
heat can pass, thus burning, or even charring, the naked skin of
the person wearing the fabric. Fabrics based on p-aramid are also
strong and resist abrasion at room temperature but also char and
shrink when exposed to flame or high temperature.
[0009] Flammable fabrics such as cotton, polyester, rayon, and
nylon have been treated with a fire retardant finish to enhance
fire retardance. While this may temporarily increase the flame
retardant properties of such fabrics, typical fire retardant
finishes are not permanent. Exposure of the treated fabric to UV
radiation (e.g., sun light) as well as routine laundering of the
fabric can greatly reduce the fire retardant properties of the
fabric. The user may then have a false sense of security, thus
unknowingly exposing himself to increased risk of burns. There may
be no objective way to determine, short of being caught in a fiery
conflagration, whether a treated garment still possesses sufficient
fire retardance to offset the risks to which the wearer may be
exposed.
[0010] More recently, a range of highly fire retardant and heat
resistant yarns and fabrics comprised of oxidized polyacrylonitrile
fibers blended with one or more strengthening fibers were
developed. Yarns and fabrics made exclusively from oxidized
polyacrylonitrile fibers lack adequate strength for use in many
applications. Blending oxidized polyacrylonitrile fibers with one
or more types of strengthening fibers yields yarns and fabrics
having increased strength and flexibility. U.S. Pat. Nos. 6,287,686
and 6,358,608 to Huang et al. disclose a range of yarns and fabrics
that preferably include about 85.5-99.9% by weight oxidized
polyacrylonitrile fibers and about 0.1-14.5% by weight of one or
more strengthening fibers. U.S. Pat. No. 4,865,906 to Smith, Jr.
includes about 25-85% oxidized polyacrylonitrile fibers combined
with at least two types of strengthening fibers. For purposes of
teaching fire retardant and heat resistant yarns, fabrics and
articles of manufacture, the foregoing patents are incorporated
herein by reference.
[0011] Highly flame retardant and heat resistant fabrics made
according to the Huang et al. patents are sold under the name
CARBONX by Chapman Thermal Products, Inc., located in Salt lake
City, Utah. Such fabrics are able to resist burning or charring
even when exposed to a direct flame. Fabrics made according to the
Huang et al. and Smith, Jr. patents are not only superior to NOMEX
as far as providing fire retardance and heat resistance, they are
softer, have higher breathability, and are better at absorbing
sweat and moisture. CARBONX feels much like an ordinary fabric made
from natural or natural feeling synthetic fibers. M-aramid fabric,
in contrast, feels more like wearing a plastic sheet than a fabric
since it does not breathe well, nor does it wick sweat and moisture
but sheds it readily. Unfortunately, the aspect of CARBONX that
makes it feel most like an ordinary fabric--its ability to absorb
sweat, moisture and liquid--does not aid in shedding a flammable
liquid.
[0012] Some applications may require a level of tensile strength,
abrasion resistance, and durability not provided by conventional
fire retardant fabrics. One way to improve such features is to
incorporate a metallic filament, such as is disclosed in U.S. Pat.
No. 6,800,367 to Hanyon et al., the disclosure of which is
incorporated by reference. Including a metal filament also
increases the cut resistance of the fabric. Nevertheless, adding a
metallic filament may increase the ability of a fabric to transfer
heat, and it does not appreciably increase the ability of the
fabric to shed flammable liquids.
[0013] Accordingly, it would be an advancement in the art to
provide fire retardant and heat resistant yarns that were able to
maintain a high level of fire retardance and heat resistance while
having improved tensile strength, abrasion resistance, durability,
and liquid shedding capabilities.
BRIEF SUMMARY OF THE INVENTION
[0014] The present invention encompasses novel yarns and fabrics
that include a high concentration of oxidized polyacrylonitrile
(O-Pan) fibers, which maintain a high level of fire retardance and
heat resistance, while also possessing improved tensile strength,
abrasion resistance, durability, and the ability to shed liquids
and gels. The inventive yarns include O-Pan fibers, typically
combined with one or more strengthening fibers, and are
encapsulated by a liquid-resistant and strengthening coating, such
as a silicone polymer. Encapsulating the fire retardant and heat
resistant yarn with a silicone polymer increases the tensile
strength, abrasion resistance, durability, and liquid and gel
shedding capability of the yarn, as well as fabrics and articles
made from such yarn. Encapsulating the yarn, rather than coating
the whole fabric, not only seals the individual yarn strands in
superior fashion, it also maintains breathability of the fabric as
a whole rather than forming an impermeable barrier. This greatly
improves performance and comfort when worn against a person's
body.
[0015] The present invention combines the tremendous fire retardant
and heat resistant characteristics of yarns made from O-Pan fibers
with the strengthening and liquid and gel shedding properties
imparted by a liquid resistant polymer coating. Simply
encapsulating the yarn of a conventional flammable fabric with a
silicone polymer coating cannot yield a fabric having a flame
retardance and heat resistance that is even remotely similar to the
level provided by O-Pan based fabrics. Moreover, encapsulating
aramid-based materials with a liquid-resistant and strengthening
silicone polymer coating does not alter the inherent tendency of
fabrics formed from such materials to char, shrink, and form holes
when exposed to direct flame and/or heated to above 600.degree. F.
Only by combining the tremendous fire retardant and heat resistant
properties of O-Pan based fabrics with the strengthening aspects
and liquid and gel shedding capabilities offered by
liquid-resistant and strengthening polymer encapsulation can true
synergy be obtained (i.e., the ability to provide the highest level
of fire retardance and heat resistance to a fabric, while also
providing enhanced tensile strength, abrasion resistance,
durability, and liquid and gel shedding capabilities, all of which
synergistically contribute to the ability of the fabric to protect
a wearer from fire and heat).
[0016] The failure to provide all of these features in a single
fabric can greatly undermine the otherwise excellent protection
from fire. For example, even though conventional CARBONX fabrics
provide superior protection against fire, heat and burns compared
to other leading fire resistant fabrics such as the leading aramid
"fire retardant" fabrics, such protection can be compromised if the
fabric lacks sufficient tensile strength, abrasion resistance and
durability for a given application. The fabric will typically only
protect the wearer to the extent the fabric is able to maintain its
structural integrity when protection is needed most, i.e., a fabric
designed to protect the skin advantageously remains positioned
between the wearer's body and the heat source to provide maximum
protection. An inadvertent hole or tear can provide a conduit
through which heat and flame can breach the otherwise continuous
protective shield. Because of the generally weaker nature of O-Pan
based fabrics compared to conventional fabrics, encapsulating the
yarn comprising O-Pan based fabrics with a strengthening polymer
provides a much greater incremental benefit with regard to tensile
strength, abrasion resistance, and durability compared to
conventional fabrics which are stronger to begin with.
Encapsulation of the O-Pan based yarn with a liquid-shedding
polymer also greatly increases the ability of the O-Pan based
fabric to shed liquids and gels, including flammable liquids and
gels.
[0017] Thus, encapsulating the yarn of O-Pan based fabrics with a
liquid-resistant and strengthening polymer reduces the tendency of
such fabrics to form holes or tears while protecting the wearer
from flame and heat, and it helps such fabrics to shed liquids and
gels, including flammable liquids and gels that can engulf the
wearer in flames if absorbed into the fabric. Encapsulation of the
O-Pan based yarn with a liquid-resistant and strengthening polymer
coating greatly increases the range of situations where O-Pan based
fabrics can provide superior protection from heat and flame as
intended, even though the liquid-shedding and strengthening polymer
may not itself provide any significant incremental heat or flame
resistance beyond that which is already provided by the O-Pan based
fabric. The high level of heat and flame resistance is provided
mainly or exclusively by the O-Pan based fabric. The encapsulation
of the O-Pan yarn comprising the fabric with a liquid-resistant and
strengthening polymer coating mainly provides the auxiliary
benefits of increased tensile strength, abrasion resistance,
durability, and liquid and gel shedding capability (e.g., flammable
liquids and gels). Nevertheless, the overall protection to the
wearer against flame and heat is greatly enhanced by the auxiliary
benefits imparted by encapsulating the yarn with a liquid-resistant
and strengthening polymer coating, demonstrating the synergistic
effect of combining O-Pan based fabrics with polymer encapsulation
of the yarn comprising the fabric.
[0018] Additional strength and abrasion resistance can be provided
by blending one or more types of strengthening fibers with the
O-Pan fibers used to make the yarn. Strengthening fibers do not
possess the level of fire retardance and heat resistance as 0-Pan
fibers but can be used to strengthened the yarn while maintaining
an adequate level of fire retardance and heat resistance in the
yarn. Exemplary "strengthening fibers" include, but are not limited
to, polybenzimidazole (PBI), polybenzoxazole (PBO),
polyphenylene-2,6-benzobisoxazole (PBO), modacrilic, p-aramid,
m-aramid, polyvinyl halides, wool, fire resistant polyesters, fire
resistant nylons, fire resistant rayons, cotton, and melamine. The
oxidized polyacrylonitrile fibers and the strengthening fibers are
each first preferably carded into respective strands or carded
together to form a blended strand. Multiple strands may then be
intertwined together to form a yarn. Alternatively, the yarn may
include strengthening filaments made from the same materials as the
foregoing strengthening fibers. Even ceramic or metal filaments may
be included, though they may be unnecessary in view of the greatly
increased tensile strength, abrasion resistance and durability
imparted by encapsulating the yarn with the liquid-shedding
polymer.
[0019] Exemplary liquid-resistant and strengthening polymer
coatings include a wide variety of curable silicone-based polymers
and polysiloxanes. Such polymers are typically encapsulated over
the individual yarn strands of a tensioned fabric that is drawn
through a bath of shear thinned polymer resin. Thereafter, the
polymer resin is cured to form the final encapsulated yarn. The
process advantageously only encapsulates the yarn strands but
leaves spaces between the yarn strands that are woven or knitted
together so as to permit the treated fabric to breathe. In this
way, the treated fabric still feels and behaves more like an
ordinary fabric rather than a laminate sheet or plugged fabric.
[0020] In general, the yarn is typically encapsulated with the
liquid-resistant and strengthening coating after being woven or
knitted into a fabric. Nevertheless, it is within the scope of the
invention to encapsulate the yarn before forming it into a fabric.
Individual yarn strands can be encapsulated by drawing them through
a bath of shear thinned polymer composition and then curing the
polymer. The treated yarn strands may then be knitted, woven or
otherwise joined together to form a desired fabric.
[0021] Examples of articles of manufacture made using the
liquid-resistant polymer treated O-Pan yarns and fabrics include
clothing, jump suits, gloves, socks, welding bibs, fire blankets,
padding, protective head gear, linings, undergarments, bedding,
drapes, and the like.
[0022] According to one embodiment, the yarn or fabric may be
pre-treated with a fluorochemical prior to encapsulation with the
shear thinned polymer coating. Pre-treatment with a fluorochemical
may assist in helping the polymer encapsulated yarn or fabric repel
or shed liquids and gels, such as water and hydrocarbons. The
fluorochemical may advantageously be applied as a suspension or
solution in combination with a solvent that is driven off by
evaporation. Thereafter, the silicone polymer is applied to the
yarn or fabric in order to encapsulate the yarn strands. The
fluorochemical is at least partially impregnated into the yarn.
[0023] These and other objects and features of the present
invention will become more fully apparent from the following
description and appended claims, or may be learned by the practice
of the invention as set forth hereinafter.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
I. Introduction and Definitions.
[0024] The present invention encompasses fire retardant and heat
resistant yarns and fabrics in which the yarn is encapsulated by a
liquid-resistant and strengthening coating to yield fabrics and
articles that provide better tensile strength, abrasion resistance,
durability, and the ability to shed liquids and gels compared to
fabrics in the absence of such yarn encapsulation. Encapsulating
the individual yarn strands, rather than coating and plugging the
whole fabric, not only seals the individual yarn strands in
superior fashion, it also maintains breathability of the
fabric.
[0025] By combining the tremendous fire retardant and heat
resistant properties of O-Pan based fabrics with the strengthening
and liquid-shedding aspects offered by encapsulation a synergistic
combination is obtained (i.e., the high level of fire retardance
and heat resistance of the fabric, coupled with enhanced tensile
strength, abrasion resistance, durability, and liquid-shedding
capabilities of the encapsulation, synergistically contribute to
the ability of the fabric to protect a wearer from fire and heat).
The failure to provide all of these features in a single fabric can
greatly undermine the otherwise excellent protection from fire,
i.e., the fabric will typically only protect the wearer to the
extent the fabric is able to maintain its structural integrity when
protection is needed most. Because of the generally weaker nature
of O-Pan based fabrics compared to conventional fabrics,
encapsulating the yarn comprising O-Pan based fabrics provides a
much greater incremental benefit with regard to tensile strength,
abrasion resistance, and durability compared to conventional
fabrics which are stronger to begin with. Encapsulation of the
O-Pan based yarn also greatly increases the ability of the O-Pan
based fabric to shed liquids and gels, including flammable liquids
and gels.
[0026] The term "Limiting Oxygen Index" (or "LOI") is defined as
the minimum concentration of oxygen necessary to support combustion
of a material. The LOI is primarily a measurement of flame
retardancy rather than temperature resistance. Temperature
resistance is typically measured as the "continuous operating
temperature".
[0027] The term "continuous operating temperature" measures the
maximum temperature, or temperature range, at which a particular
fabric will maintain its strength and integrity over time when
exposed to constant heat of a given temperature or range. For
instance, a fabric that has a continuous operating temperature of
400.degree. F. can be exposed to temperatures of up to 400.degree.
F. for prolonged periods of time without significant degradation of
fiber strength, fabric integrity, and protection of the user. In
some cases, a fabric having a continuous operating temperature of
400.degree. F. may be exposed to brief periods of heat at higher
temperatures without significant degradation. The presently
accepted standard for continuous operating temperature in the auto
racing industry rates fabrics as being "flame retardant" if they
have a continuous operating temperature of between 375.degree. F.
to 600.degree. F.
[0028] The term "fire retardant" refers to a fabric, felt, yarn or
strand that is self extinguishing. The term "nonflammable" refers
to a fabric, felt, yarn or strand that will not burn.
[0029] The term "Thermal Protective Performance" (or "TPP") relates
to a fabric's ability to provide continuous and reliable protection
to a person's skin beneath a fabric when the fabric is exposed to a
direct flame or radiant heat. The TPP measurement, which is derived
from a complex mathematical formula, is often converted into an SFI
rating, which is an approximation of the time it takes before a
standard quantity of heat causes a second degree burn to occur.
[0030] The term "SFI Rating" is a measurement of the length of time
it takes for someone wearing a specific fabric to suffer a second
degree burn when the fabric is exposed to a standard temperature.
The SFI Rating is printed on a driver's suit. The SFI Rating is not
only dependent on the number of fabric layers in the garment, but
also on the LOI, continuous operating temperature and TPP of the
fabric or fabrics from which a garment is manufactured. The
standard SFI Ratings are as follows:
TABLE-US-00001 SFI Rating Time to Second Degree Burn 3.2A/1 3
Seconds 3.2A/3 7 Seconds 3.2A/5 10 Seconds 3.2A/10 19 Seconds
3.2A/15 30 Seconds 3.2A/20 40 Seconds
[0031] A secondary test for flame retardance is the after-flame
test, which measures the length of time it takes for a flame
retardant fabric to self extinguish after a direct flame that
envelopes the fabric is removed. The term "after-flame time" is the
measurement of the time it takes for a fabric to self extinguish.
According to SFI standards, a fabric must self extinguish in 2.0
seconds or less in order to pass and be certifiably "flame
retardant".
[0032] The term "tensile strength" refers to the maximum amount of
stress that can be applied to a material before rupture or failure.
The "tear strength" is the amount of force required to tear a
fabric. In general, the tensile strength of a fabric relates to how
easily the fabric will tear or rip. The tensile strength may also
relate to the ability of the fabric to avoid becoming permanently
stretched or deformed. The tensile and tear strengths of a fabric
should be high enough so as to prevent ripping, tearing, or
permanent deformation of the garment in a manner that would
significantly compromise the intended level of thermal protection
of the garment.
[0033] The term "abrasion resistance" refers to the tendency of a
fabric to resist fraying and thinning during normal wear. Although
related to tensile strength, abrasion resistance also relates to
other measurements of yarn strength, such as shear strength and
modulus of elasticity, as well as the tightness and type of the
weave or knit.
[0034] The terms "fiber" and "fibers" refers to any slender,
elongated structure that can be carded or otherwise formed into a
thread. Fibers typically have a length of about 2 mm to about 25 mm
and an aspect ratio of at least about 100:1. Examples include
"staple fibers", a term that is well-known in the textile art. The
term "fiber" differs from the term "filament", which is defined
separately below and which comprises a different component of the
inventive yarns.
[0035] The term "thread", as used in the specification and appended
claims, shall refer to continuous or discontinuous elongated
strands formed by carding or otherwise joining together one or more
different kinds of fibers.
[0036] The term "filament" shall refer to a thread of indefinite
length, whether comprising multiple fibers or a monofilament.
[0037] The term "yarn" shall refer to a continuous strand comprises
of a multiplicity of fibers, filaments, or the like in bundled
form, such as may be suitable for knitting, weaving or otherwise
used to form a fabric.
[0038] The term "fabric" shall refer to an article of manufacture
formed by knitting, weaving or otherwise joining a plurality of
yarn strands together to form a multi-dimensional structure used to
manufacture a wide variety of useful articles.
[0039] The terms "encapsulate" and "outer shell" shall refer to the
positioning or placement of a liquid-shedding polymer material
around an inner core comprising a yarn strand, before or after the
yarn is formed into a fabric. The terms "encapsulate" and "outer
shell" refer to the fact that at least some of the liquid-shedding
polymer material is located on an outer perimeter of the yarn
strand(s). They do not mean that some of the liquid-shedding
polymer material that "encapsulates" the inner yarn core cannot
also be located in interstitial spaces or pores within the inner
yarn core.
[0040] The term "inner core" shall refer to the fire retardant and
heat resistant yarn that is encapsulated by the liquid-resistant
and strengthening polymer shell comprising the "outer shell".
II. Fire Retardant and Heat Resistant Yarns and Fabrics.
[0041] Fire retardant and heat resistant yarns according to the
invention typically comprise at least one type of fire retardant
and heat resistant fibers and/or filaments, preferably combined or
blended with at least one type of strengthening fibers and/or
filaments. Fire retardant and heat resistant fibers can be carded
into a thread, either alone or in combination with one or more
types of strengthening fibers. Multiple threads can be twisted or
braided together to form a yarn strand. One or more fire retardant
and heat resistant threads comprising mainly or solely fire
retardant and heat resistant fibers or filament(s) can be twisted
or braided together with one or more strengthening strands
comprising mainly or solely strengthening fibers and/or
filament(s). Because a yarn strand typically consists of multiple
strands twisted or braded together, it will typically include a
substantial amount of interstitial space between the individual
strands, at least before being encapsulated by the liquid-shedding
polymer.
[0042] Fabrics comprising the fire retardant and heat resistant
yarns can be formed by knitting, weaving or otherwise combining
multiple strands of yarn together. Any known method of forming a
fabric from a yarn can be utilized to form the inventive fire
retardant and heat resistant fabrics. Exemplary fire retardant and
heat resistant yarns, fabrics and articles that can be improved
according to the present invention are disclosed in U.S. Pat. Nos.
6,287,686, 6,358,608, 6,800,367 and 4,865,906. For purposes of
disclosing fire retardant and heat resistant yarns and fabrics
capable of being encapsulated according to the invention, the
disclosures of the foregoing patents are incorporated by
reference.
[0043] A. Fire Retardant and Heat Resistant Fibers and
Filaments
[0044] Exemplary fire retardant and heat resistant fibers and
filaments are made from oxidized polyacrylonitrile (O-Pan). The
O-Pan fibers or filaments within the scope of the invention may
comprise any type of O-Pan having high fire retardance and heat
resistance. In a preferred embodiment, O-Pan is obtained by heating
polyacrylonitrile (e.g., polyacrylonitrile fibers or filaments) in
a cooking process between about 180.degree. C. to about
3000.degree. C. for at least about 120 minutes. This
heating/oxidation process is where the polyacrylonitrile receives
its initial carbonization. Preferred O-Pan fibers and filaments
have an LOI of about 50-65. In most cases, O-Pan made in this way
may be considered to be nonflammable.
[0045] Examples of suitable O-Pan fibers include LASTAN,
manufactured by Ashia Chemical in Japan; PYROMEX, manufactured by
Toho Rayon in Japan; PANOX, manufactured by SGL; and PYRON,
manufactured by Zoltek. It is also within the scope of the
invention to utilize filaments that comprise O-Pan.
[0046] In general, it is believed that fabrics which include a
substantial amount of O-Pan fibers and/or filaments will resist
burning, even when exposed to intense heat or flame exceeding
3000.degree. F., because the O-Pan fibers carbonize and expand,
thereby eliminating any oxygen content within the fabric necessary
for combustion of the more readily combustible strengthening
fibers. In this way, the O-Pan fibers or filaments provide a
combustion shield that makes the less fire retardant substances in
the yarn or fabric act like better fire retardant substances.
[0047] One of skill in the art will appreciate that other fire
retardant and heat resistant materials can be used in addition to,
or in place of, O-Pan so long as they have fire retardant and heat
resistance properties that are comparable to those of O-Pan. By way
of example, polymers or other materials having an LOI of at least
about 50 and which do not burn when exposed to heat or flame having
a temperature of about 3000.degree. F. could be used in addition
to, or instead of, O-Pan.
[0048] The fire retardant and heat resistant yarn comprising the
inner core of the overall liquid and gel shedding yarn, fabric or
article may consist solely of O-Pan fibers or filaments. When the
O-Pan is blended with one or more strengthening fibers or
filaments, O-Pan is preferably included in an amount in a range of
about 25% to about 99.9% by weight of the inner core, more
preferably in a range of about 40% to about 95% by weight, and most
preferably in a range of about 50% to about 90% by weight of the
inner core.
[0049] B. Strengthening Fibers and Filaments
[0050] Strengthening fibers and filaments that may be incorporated
into fire retardant and heat resistant yarns, fabrics and articles
of the present invention may comprise any fiber or filament known
in the art. In general, preferred strengthening fibers will be
those that have a relatively high LOI and TPP compared to natural
organic fibers such as cotton, although the use of such fibers is
within the scope of the invention. The strengthening fibers
preferably have an LOI greater than about 20.
[0051] Strengthening fibers may be carded or otherwise formed into
threads, either alone or in combination with other fibers (e.g,
O-Pan fibers). Strengthening threads or filaments may be twisted,
braided or otherwise combined with fire retardant and heat
resistant strands to form a blended yarn.
[0052] Strengthening fibers and filaments within the scope of the
invention include, but are not limited to, polybenzimidazole (PBI),
polybenzoxazole (PBO), polyphenylene-2,6-benzobisoxazole (PBO),
modacrilic, p-aramid, m-aramid, polyvinyl halides, wool, fire
resistant polyesters, fire resistant nylons, fire resistant rayons,
cotton, linen, and melamine. By way of comparison with O-Pan, which
has an LOI of about 50-65, the LOI's of selected strengthening
fibers are as follows:
TABLE-US-00002 PBO 68 PBI 35 36 modacrylic 28 32 m-Aramid 28 36
p-Aramid 27 36 wool 23 polyester 22 23 nylon 22 23 rayon 16 17
cotton 16 17
[0053] Examples of suitable p-aramids include KEVLAR, manufactured
by DuPont; TWARON, manufactured by Twaron Products BB; and
TECKNORA, manufactured by Teijin. Examples of suitable m-aramids
include NOMEX, manufactured by DuPont; CONEX, manufactured by
Teijin; and P84, an m-aramid yarn with a multi-lobal cross-section
made by a patented spinning method, manufactured by Inspec Fiber.
For this reason P84 has better fire retardant properties compared
to NOMEX.
[0054] An example of a PBO is ZYLON, manufactured by Toyobo. An
example of a PBI fiber is CELAZOLE of PBI Performance Products,
Inc. An example of a melamine fiber is BASOFIL. An example of a
fire retardant or treated cotton is PROBAN, manufactured by Westex.
Another is FIREWEAR.
[0055] Strengthening fibers and filaments may be incorporated in
the yarns of the present invention in at least the following ways:
(1) as one or more strengthening filaments twisted, wrapped,
braided or otherwise joined together with threads or filaments
comprising oxidized polyacrylonitrile; or (2) as fibers blended
with O-Pan fibers into one or more threads.
[0056] In short, strengthening fibers may be added to the inventive
yarns in the form of strengthening threads comprising one or more
different types of strengthening fibers, a ended thread comprising
O-Pan fibers and one or more different types of strengthening
fibers, or as a strengthening filament. When O-Pan is blended with
one or more strengthening fibers or filaments, the strengthening
fibers or filaments are preferably included in an amount in a range
of about 0.1% to about 75% by weight of the inner core, more
preferably in a range of about 5% to about 60% by weight, and most
preferably in a range of about 10% to about 50% by weight of the
inner core.
[0057] C. Metallic and Ceramic Filaments
[0058] Yarns according to the invention may include one or more
types of metallic or ceramic filaments in order to increase cut
resistance, tensile strength and abrasion resistance. Metallic
filaments typically have the highest combination of tensile
strength and cut resistance but also conduct heat more rapidly.
Examples of metals used to form high strength filaments include,
but are not limited to, stainless steel, stainless steel alloys,
other steel alloys, titanium, aluminum, copper, and the like.
[0059] Examples of high strength ceramic filaments include silicon
carbide, graphite, silica, aluminum oxide, other metal oxides, and
the like. Examples of high strength and heat resistant ceramic
filaments are set forth in U.S. Pat. Nos. 5,569,629 and 5,585,312
to TenEyck et al., which disclose ceramic filaments that include
62-85% by weight SiO.sub.2, 5-20% by weight Al.sub.2O.sub.3, 5-15%
by weight MgO, 0.5-5% by weight TiO.sub.x, and 0-5% ZrO.sub.2. High
strength and flexible ceramic filaments based on a blend of one or
oxides of Al, Zr, Ti, Si, Fe, Co, Ca, Nb, Pb, Mg, Sr, Cu, Bi and Mn
are disclosed in U.S. Pat. No. 5,605,870 to Strom-Olsen et al. For
purposes of disclosing high strength ceramic filaments, the
foregoing patents are incorporated herein by reference. Fiberglass
filaments can also be used. Strengthening filaments preferably have
a diameter in a range of about 0.0001'' to about 0.01'', more
preferably in a range of about 0.0005'' to about 0.008'', and most
preferably in a range of about 0.001'' to about 0.006''. Yarns
containing a high concentration of oxidized polyacrylonitrile
fibers that are generally too weak to be used in the manufacture of
fire retardant and heat resistant fabrics can be greatly
strengthened with even small percentages of one or more metallic
filaments, and fabrics manufactured therefrom have been found to be
surprisingly strong.
[0060] In general, where it is desired to maximize the strength of
the material, it will be preferable to maximize the volume of
strengthening filaments that are added to the yarn. However, it
will be appreciated that as the amount of strengthening filaments
increases in the yarn, the heat resistance generally declines. As a
practical matter, the fire retardant and heat resistant
requirements of the resulting yarn, fabric or other fibrous blend
will determine the maximum amount of strengthening filaments that
can be added to the yarn.
III. Liquid-Shedding and Strengthened Fire Retardant and Heat
Resistant Yarns and Fabrics.
[0061] The fire retardant and heat resistant yarns and fabrics
discussed above can be treated according to the invention by
encapsulating the yarn with a liquid-shedding and strengthening
polymer coating material. The liquid-shedding and strengthening
polymer coating yields yarns, fabrics and articles that are much
better at shedding liquids and gels, such as flammable liquids and
gels. In this way, thermal protection to the wearer is further
increased when used to protect a wearer exposed to flammable
liquids or gels. In addition, polymer encapsulation significantly
increases the tensile strength, abrasion resistance and durability
of the first retardant and heat resistant yarns, fabrics and
articles of the invention. Increasing the tensile strength,
abrasion resistance and durability of a fabric or article also
increases the thermal protection of the wearer by reducing the
formation of holes or rips through the fabric and increasing the
continuity of protection.
[0062] Exemplary liquid-shedding and strengthening polymer
materials, optional compositions applied to yarns in addition to
the liquid-shedding and strengthening polymer materials, as well as
methods for encapsulating yarns with the liquid-shedding and
strengthening polymer materials, are disclosed in U.S. Pat. Nos.
4,666,765, 5,004,643, 5,209,965, 5,418,051, 5,856,245, 5,869,172,
5,935,637, 6,040,251, 6,071,602, 6,083,602, 6,129,978, 6,289,841,
6,312,523, 6,342,280, and 6,416,613. For purposes of disclosing
liquid-shedding and strengthening polymer coating materials, as
well as methods of applying such materials to a fabric, the
disclosures of the foregoing patents are incorporated by
reference.
[0063] Exemplary liquid-resistant and strengthening polymer
coatings include a wide variety of curable silicone-based polymers
and polysiloxanes. Such polymers are typically applied as an
uncured or partially cured polymer resin and then cured (i.e.,
cross-linked and/or further polymerized) after encapsulating the
yarn being treated. The polymer resins before application typically
have a viscosity in a range of about 1000 cps to about 2,000,000
cps at a shear rate of 1/10 s and a temperature of 25.degree. C.
The polymer resins preferably have a viscosity in a range of about
5000 cps to about 10,000 cps at a shear rate of 1/10 s and a
temperature of 25.degree. C. In a most preferred embodiment, such
polymer resins preferably contain less than about 1% by weight of
volatile material. When cured, the encapsulating polymers are
preferably elastomeric in order to yield a generally flexible yarn,
fabric or article.
[0064] A preferred class of liquid curable silicone polymer
compositions comprises a curable mixture of the following
components: (1) at least one organo-hydrosilane polymer or
copolymer; (2) at least one vinyl substituted polysiloxane polymer
or copolymer; (3) a platinum or platinum containing catalyst; and
(4) optionally fillers and additives.
[0065] Typical silicone hydrides (component 1) are
polymethylhydrosiloxanes which are dimethyl siloxane copolymers.
Typical vinyl terminated siloxanes are vinyl-dimethyl terminated or
vinyl substituted polydimethyl siloxanes. Typical catalyst systems
include solutions or complexes of chloroplatinic acid in alcohols,
ethers, divinylsiloxanes, and cyclic vinyl siloxanes.
[0066] Particulate fillers can be included to extend and reinforce
the cured polymer composition and also improve the thixotropic
behavior of the uncured polymer resins.
[0067] Exemplary silicone polymer resins that may be used to
encapsulate fire retardant and heat resistant yarns according to
the invention include, but are not limited to, SILOPREN LSR 2530
and SILOPREN LSR 2540/01, which comprise a vinyl-terminated
polydimethyl/siloxane with fumed silica and methylhydrogen
siloxane, which are available from Mobay Chemical Co.; SILASTIC 595
LSR, a polysiloxane available from Dow Corning; SLE 5100, SLE 5110,
SLE 5300, SLE 5500, and SLE 6108, which are polysiloxanes, and SLE
5106, a siloxane resin solution, all available from General
Electric; KE 1917 and DI 1940-30, silicone polymers available from
Shin-Etsu; LIQUID RUBBER BC-10, a silicone fluid with silicone
dioxide filler and curing agents, available from SWS Silicones
Corporation.
[0068] The foregoing silicone polymer resins are characterized as
having high viscosity. In order for such polymer resins to properly
encapsulate the yarn, they must typically be thinned in some manner
to reduce the viscosity so as to flow around the yarn and at least
partially penetrate into the interstitial spaces within the yarn.
This may be accomplished in any desired manner. According to one
embodiment, the polymer resins are subjected to high shearing
conditions, which causes them to undergo shear thinning and/or
thixotropic thinning. Any suitable mixing blade, combination of
blades, or other apparatus capable of applying high shear may be
introduced into the vessel containing the polymer resin in order to
temporarily reduce the viscosity of the resin before or during
application to the yarn or fabric.
[0069] Such polymers are typically encapsulated over the individual
yarn strands of a tensioned fabric that is drawn through a bath of
shear and/or thixotropically thinned polymer resin. Thereafter, the
polymer resin is cured to form the final encapsulated yarn. Curing
may be carried out using heat to accelerate polymerization and/or
cross-linking or the polymer resin. The process advantageously only
encapsulates the yarn strands but leaves spaces between the yarn
strands that are woven or knitted together so as to permit the
treated fabric to breathe. In this way, the treated fabric still
feels and behaves more like an ordinary fabric rather than a
laminate sheet or plugged fabric.
[0070] According to one embodiment, the silicone polymer resin is
blended with a benzophenone (e.g., about 0.3-10 parts by weight of
the silicone polymer), examples of which include
2,4-dihydroxybenzophenone (e.g., UVINUL 400, available from BASF),
2-hydroxy-4-methoxybenzophenone (e.g., UVINUL M-40, available from
BASF), 2,2',4,4'-tetrahydroxybenzophenone (e.g., UVINUL D-50,
available from BASF), 2,2'-dihydroxy-4,4'-dimethoxybenzophenone
(e.g., UVINUL D-49, available from BASF), mixed tetra-substituted
benzophenones (e.g., UVINUL 49 D, available from BASF), and
2-ethylhexyl-2-cyano-3,3-diphenylacrylate (e.g., UVINUL N-539,
available from BASF).
[0071] The silicone polymer resin may also be blended with an
accelerator (e.g., Dow Corning 7127 accelerator, a proprietary
polysiloxane material) (e.g., 5-10 parts by weight of the silicone
polymer resin) just before being applied to the yarn or fabric to
promote curing.
[0072] The silicone polymer resin may further include various
additives in order to impart desired properties to the yarn or
fabric. Exemplary additives include UV absorbers, flame retardants,
aluminum hydroxide, filling agents, blood repellants, flattening
agents, optical reflective agents, hand altering agents,
biocompatible proteins, hydrolyzed silk, and agents that affect
thermal conductivity, radiation reflectivity, and/or electrical
conductivity.
[0073] In general, the yarn is typically encapsulated with the
liquid-resistant coating after being woven or knitted into a
fabric. Nevertheless, it is within the scope of the invention to
encapsulate the yarn before forming it into a fabric. One or more
individual yarn strands can be encapsulated by drawing them through
a bath of shear thinned polymer composition and then curing the
polymer. The treated yarn strands may then be knitted, woven or
otherwise joined together to form a desired fabric.
[0074] The silicone polymer coating is preferably applied to the
yarn or fabric in an amount in a range of about 5% to about 200% by
weight of the original yarn or fabric inner core, more preferably
in an amount in a range of about 10% to about 100% by weight of the
original yarn or fabric inner core.
[0075] Yarns and fabrics may also be advantageously pre-treated
with a fluorochemical prior to being encapsulated by the silicone
polymer resin in order to further increase the liquid and gel
shedding properties of the yarn or fabric. Exemplary fluorochemical
compositions include, but are not limited to, MILEASE F-14N, F-34,
F-31.times. and F-53 sold by ICI Americas, Inc.; PHOTOTEX FC104,
FC461, FC731, FC208 AND FC232 sold by Ciba/Geigy; TEFLON polymers
such as TEFLON G, NPA, SKF, UP, UPH, PPR, N and MLV, sold by
DuPont; ZEPEL polymers such as ZEPEL B, D, K, RN, RC, OR, HT, 6700
AND 7040, also from DuPont; SCOTCHGUARD sold by 3M.
[0076] MILEASE F-14 contains approximately 18% perfluoroacrylate
copolymer, 10% ethylene glycol, 7% acetone, and 65% water. MILEASE
F-31X is a dispersion of fluorinated resin, acetone and water.
ZEPEL 6700 is comprised of 15-20% perfluoroalkyl acrylic copolymer,
1-2% alkoxylated carboxylic acid, 3-5% ethylene glycol, and water,
and has a pH of 2-5. ZEPEL 7040 is similar to ZEPEL 6700 but
further contains 7-8% acetone. SCOTCHGUARD is comprised of
aqueously dispersed fluorochemicals in polymeric form.
[0077] Liquid repellant fluorochemical compositions are saturated
into the fabric or yarn to completely and uniformly wet the fabric
or yarn. This may be performed by dipping the fabric or yarn in a
bath of liquid composition or padding the composition onto and into
the fabric or yarn. After applying the fluorochemical composition
to the fabric or yarn, the water (or other liquid carrier) and
other volatile components of the composition are removed by
conventional techniques to provide a treated fabric or yarn that is
impregnated with the dried fluorochemical. In one embodiment, the
saturated fabric or yarn is compressed to remove excess
composition. It is then heated to remove the carrier liquid by
evaporation (e.g., at a temperature of about 130-160.degree. C. for
a period of time about 2-5 minutes). If the fluorochemical is
curable, heating may also catalyze Oz or trigger curing.
[0078] The fluorochemical may also contain a bonding agent in order
to strengthen the bond between the fluorochemical and the yarn or
fabric to which it is applied. Exemplary bonding agents include
Mobay SILOPREN bonding agent type LSR Z 3042 and NORSIL 815
primer.
[0079] When included, the fluorchemical is preferably applied in an
amount in a range of about 1% to about 10% by weight of the
original yarn or fabric inner core, more preferably in an amount in
a range of about 2% to about 4% by weight of the original yarn or
fabric inner core.
IV. EXAMPLES
[0080] The following examples are provided in order to illustrate
various embodiments of the invention. Although the examples are
written in present tense and are therefore hypothetical in nature,
they are based on testing of a fabric comprising a 70:30 wt % blend
of O-Pan and p-aramid that was coated with a proprietary
silicone-based polymer coating owned by Nextec Applications Inc.,
based in Vista, Calif. at the request of the inventor. The examples
therefore have a high degree of predictive value based on test
results conducted by the inventor.
Example 1
[0081] A fire retardant and heat resistant fabric made from a yarn
having a 70:30 wt % blend of O-Pan and p-aramid, respectively, is
encapsulated with a liquid shedding and strengthening
silicone-based polymer as follows. First, the fabric is placed
under tension. Second, the tensioned fabric is drawn through a
vessel containing a silicone-based polymer resin. Third, the
silicone-based polymer resin is subjected to localized
shear-thinning forces produced by a rapidly spinning shearing blade
adjacent to a surface of the fabric in order for the shear-thinned
resin to encapsulate the yarn of the fabric and at least partially
penetrate into interstitial spaces of the yarn. The viscosity of
the silicone-based polymer resin is sufficiently low that it does
not plug the spaces between the individual yarn strands of the
fabric. Fourth, the treated tensioned fabric is removed from the
vessel containing the silicone-based polymer resin. Fifth, the
treated fabric is heated in order to cure the silicone-based
polymer resin and form the strengthening and liquid-shedding
coating over the yarn.
[0082] The resulting fire retardant and heat resistant fabric
comprising silicone polymer encapsulated yarn has increased tensile
strength, abrasion resistance, durability and liquid- and
gel-shedding capability compared to the fire retardant and heat
resistant fabric in the absence of the silicone polymer. The fabric
is therefore better able to protect a person wearing the fabric
when exposed to fire, heat and a flammable liquid or gel compared
to the fire retardant and heat resistant fabric prior to being
encapsulated with the silicone polymer by better shedding the
flammable liquid or gel and resisting formation of holes through
the fabric, thus providing greater continuity of fabric between the
wearer's skin and the fire, heat and any remaining flammable liquid
or gel. Because the silicone polymer only encapsulates the
individual yarn strands comprising the fabric, but does not plug
the holes or spaces between the yarn strands, the treated fabric
remains porous and is able to breathe.
Example 2
[0083] A fire retardant and heat resistant fabric made from a yarn
having a 60:20:20 wt % blend of O-Pan, p-aramid, and m-aramid,
respectively, is treated in the manner discussed in Example 1. The
resulting fabric is somewhat stronger and more durable than the
fabric obtained in Example 1 as a result of including a blend of
strengthening fibers.
Example 3
[0084] A fire retardant and heat resistant fabric made from a yarn
consisting of 100% O-Pan is treated in the manner discussed in
Example 1. Even though the fabric made from 100% O-Pan is
relatively weak and fragile, treatment with the silicone polymer
greatly increases the tensile strength, abrasion resistance, and
durability so as to be acceptable for applications for which the
fabric would otherwise be unacceptable absent the encapsulation
treatment.
Example 4
[0085] A fire retardant and heat resistant fabric made from a yarn
having a 40:20:20:20 wt % blend of O-Pan, p-aramid, fire retardant
wool, and PBI, respectively, is treated in the manner discussed in
Example 1. This fabric is significantly stronger to begin with
compared to the fabrics of Examples 1-3 as a result of include more
strengthening fibers, but is less fire retardant and heat
resistant.
Example 5
[0086] A fire retardant and heat resistant fabric made from a yarn
having a 60:40 wt % blend of O-Pan and m-aramid, respectively, is
treated in the manner discussed in Example 1. This fabric is
significantly stronger to begin with compared to the fabrics of
Example 1 as a result of include more strengthening fibers, but is
less fire retardant and heat resistant.
Example 6
[0087] A fire retardant and heat resistant fabric made from a yarn
having a 90:10 wt % blend of O-Pan and PBI, respectively, is
treated in the manner discussed in Example 1. This fabric is not as
strong as compared to the fabrics of Examples 1, 2, 4 and 5 as a
result of including less strengthening fibers, but is more fire
retardant and heat resistant as a result of including 10% PBI.
Encapsulating this blend with the silicone polymer coating greatly
enhances its strength.
Example 7
[0088] A fire retardant and heat resistant fabric made from a yarn
having a 60:10:15:15 wt % blend of O-Pan, p-aramid, polyvinyl
chloride, and m-aramid, respectively, is treated in the manner
discussed in Example 1. This fabric is quite stronge as compared to
previous examples as a result of including more and more types of
strengthening fibers, but is less fire retardant and heat
resistant.
Examples 8-14
[0089] The fire retardant and heat resistant fabrics of Examples
1-7 are pretreated with a fluorochemical prior to encapsulation
with the silicone polymer. The flurochemical is saturated into the
fabric as a solution or suspension with a solvent. Excess
flurochemical composition is removed from the saturated fabric by
applying pressure. Thereafter, the flurochemical composition is
heated in order to remove the solvent by evaporation and dry the
flurochemical. After applying the silicone polymer according to
Example 1, the flurochemical remains at least partially impregnated
within the fire retardant and heat resistant fabric.
[0090] The flurochemical further enhances the liquid- and
gel-shedding properties of the fire retardant and heat resistant
fabric beyond what is provided by the silicone polymer
encapsulation provided in Examples 1-7. Enhancing the liquid- and
gel-shedding properties of the fire retardant and heat resistant
fabric further protects a wearer of the fabric from fire and heat
if doused with a flammable liquid or gel, such as gasoline.
Examples 15-33
[0091] Various treated fire retardant and heat resistant fabrics
are manufactured using any of the fabrics utilized in Examples 1-7.
The silicone polymer coating used to treat the fire retardant and
heat resistant fabric(s) according to Examples 15-33 are set forth
in Table I below. The amount of silicone resin in the polymer
coating is in all cases 100-parts. The "mixture ratio" refers to
the ratio of packaged components as supplied by the
manufacturer.
TABLE-US-00003 TABLE I Mix- Substituted Exam- Silicone ture Benzo-
Other ple Resin Ratio phenone Parts Additives Part 15 Silopren
.RTM. 1:1 Uvinul 400 5 7127 5/10 LSR 2530 Accelerator.sup.1 16
Silastic .RTM. 1:1 Uvinul 400 5 Syl-off .RTM. 50 595 LSR 7611.sup.2
17 SLE 5100, 10:1 Uvinul 400 5 Sylox .RTM. 2.sup.3 8 Liquid BC- 1:1
10 18 Silopren .RTM. 1:1 Uvinul 400 5 Hydral .RTM. 10 LSR 2530
710.sup.4 19 Silopren .RTM. 1:1 Uvinul 400 5 Silopren .RTM. 1 LSR
1530 LSR Z3042.sup.5 20 SLE 5500 10:1 Uvinul 400 5 21 Silopren
.RTM. 1:1 Uvinul 400 5 2430 22 SLE 5300 10:1 Uvinul 400 5 23 SLE
5106 10:1 Uvinul 400 5 24 Silopren .RTM. 1:1 Uvinul 400 5
Flattening 4 LSR 2530 Agent OK412 .RTM..sup.6 25 Silopren .RTM. 1:1
Uvinul 400 5 Nalco .RTM. 50 LSR 2530 1SJ-612 Colloidal Silica.sup.7
26 Silopren .RTM. 1:1 Uvinul 400 5 Nalco .RTM. 50 LSR 2530 1SJ-612
Colloidal Alumina.sup.8 27 Silastic .RTM. 1:1 Uvinul 400 5 200
Fluid.sup.9 7 595 LSR 28 Silopren .RTM. 1:1 Uvinul 400 5 LSR 2530
29 Silastic .RTM. 1:1 Uvinul 400 5 Zepel .RTM. 3 595 LSR
7040.sup.10 30 Silastic .RTM. 1:1 Uvinul 400 5 Zonyl .RTM. 1/10 595
LSR UR.sup.11 31 Silastic .RTM. 1:1 Uvinul 400 5 Zonyl .RTM. 1/10
595 LSR FSN-100.sup.12 32 Silopren .RTM. 1:1 Uvinul 400 5 DLX- 5
LSR 2530 600 .RTM..sup.13 33 Silopren .RTM. 1:1 Uvinul 400 5 TE- 5
LSR 2530 3608 .RTM..sup.14 .sup.17127 Accelerator (Dow Corning) is
a polysiloxane .sup.2Syl-off .RTM. (Dow Corning) is a cross-linker
.sup.3Sylox .RTM. 2 (W. R. Grace & Co.) is a synthetic
amorphous silica .sup.4Hydral .RTM. 710 (Alcoa) is a hydrated
aluminum oxide .sup.5Silopren .RTM. LSR Z3042 (Mobay) is a silicone
primer (bonding agent) mixture .sup.6Flattening Agent OK412 .RTM.
(Degussa Corp.) is a wax coated silicon dioxide .sup.7Nalco .RTM.
1SJ-612 Colloidal Silica (Nalco Chemical Co.) is an aqueous
solution of silica and alumina .sup.8Nalco .RTM. 1SJ-612 Colloidal
Alumina (Nalco Chemical Co.) is an aqueous colloidal alumina
dispersion .sup.9200 Fluid (Dow Corning) is a 100 cps viscosity
dimethylpolysiloxane .sup.10Zepel .RTM. 7040 (DuPont) is a nonionic
fluoropolymer .sup.11Zonyl .RTM. UR (DuPont) is an anionic
fluorosurfactant .sup.12Zonyl .RTM. FSN-100 (DuPont) is a nonionic
fluorosurfactant .sup.13DLX-600 .RTM. (DuPont) is a
polytetrafluoroethylene micropowder .sup.14TE-3608 .RTM. (DuPont)
is a polytetrafluoroethylene micropowder
[0092] The silicone polymer resin and other components are mixed
using a Hockmayer F dispersion blade at low torque and high shear.
The fire retardant and heat resistant fabric is tensioned and
passed through a bath containing the silicone resin composition.
Localized high shear is applied to the silicone resin composition
near the surface of the fabric in order to coat the yarn strands
comprising the fabric at a rate of 1.0 oz/sq. yd. The fabric is
passed through the polymer resin composition several times to
ensure thorough impregnation. After impregnation, the impregnated
fabric is removed from the silicone polymer composition bath and
passed through a line oven of approximately 10 yards in length, as
4-6 yards per minute, and cured at a temperature of 325-350.degree.
F.
Examples 34-60
[0093] Various treated fire retardant and heat resistant fabrics
are manufactured according to any of Examples 8-14. The
fluorochemical compositions used to pretreat the fire retardant and
heat resistant fabric(s) according to Examples 34-60 prior to
application of the silicone resin composition (which may comprise
any of the compositions of Examples 15-33 in Table I) are set forth
in Table II below.
TABLE-US-00004 TABLE II Example Flurochemical 34 Milease .RTM.
F-14N 35 Milease .RTM. F-34 36 Milease .RTM. F-31X 37 Milease .RTM.
F-53 38 Phobotex .RTM. FC104 39 Phobotex .RTM. FC461 40 Phobotex
.RTM. FC731 41 Phobotex .RTM. FC208 42 Phobotex .RTM. FC232 43
Teflon .RTM. G 44 Teflon .RTM. NPA 45 Teflon .RTM. SKF 46 Teflon
.RTM. UP 47 Teflon .RTM. UPH 48 Teflon .RTM. PPR 49 Teflon .RTM. N
50 Teflon .RTM. MLV 51 Zepel .RTM. B 52 Zepel .RTM. D 53 Zepel
.RTM. K 54 Zepel .RTM. RN 55 Zepel .RTM. RC 56 Zepel .RTM. OR 57
Zepel .RTM. HT 58 Zepel .RTM. 6700 59 Zepel .RTM. 7040 60
Scotchguard .RTM.
[0094] Prior to applying the fluorochemical composition, the fire
retardant and heat resistant fabric is washed with detergent,
rinsed thoroughly, and hung to air dry. Thereafter, the fabric is
soaked in water and then wrung dry to retain 0.8 g water/g fabric.
The fabric is then treated with a solution or suspension (e.g., a
2% solution) of the fluorochemical composition, taking into account
the water already soaked into the fabric (e.g., using a 2.5%
solution of the fluorochemical). The pretreated fabric is wrung
through a wringer and air dried. The fabric is then heated in an
oven for 1 minute at 350.degree. F. to remove any remaining solvent
and sinter the fluorochemical. The fluorochemical treated fabric is
then coated with a silicone polymer composition (e.g., a
composition from one of Example 15-33.
Example 61
[0095] Various treated liquid- and gel-shedding and strengthened
fire retardant and heat resistant fabrics are manufactured using
the fabrics disclosed in Examples 1-7, the silicone resin
compositions of Examples 15-33, and the fluorochemical compositions
of Examples 34-60 (i.e., a wide range of different liquid- and
gel-shedding and strengthened fire retardant and heat resistant
fabrics are manufactured using every possible combination of
fabrics, silicone resin compositions, and fluorochemical
compositions of Examples 1-7, 15-33 and 34-60, respectively).
[0096] The fire retardant and heat resistant fabrics treated
according to the foregoing examples have increased tensile
strength, abrasion resistance, durability and liquid- and
gel-shedding properties compared to the fabrics prior to treating
with the silicone-based polymer. Because the silicone-based polymer
only encapsulates the individual yarn strands but not the pores or
spaces between the overlapping yarn strands, the treated fabrics
retain a level of breathability and porosity. In addition, the
elastomeric properties of the silicone-based polymer allow the
fabrics to retain a level of flexibility and suppleness, which
helps maintain the comfort of the fabrics if worn against a
person's body.
[0097] The fabrics can be used in the manufacture of a wide variety
of clothing and other articles where high fire retardance, heat
resistance, and liquid and gel shedding capabilities are desirable.
Examples include, but are not limited to, clothing, jump suits,
gloves, socks, welding bibs, fire blankets, padding, protective
head gear, linings, undergarments, bedding, drapes, and the like.
The treated fabrics and articles are especially useful in the case
where the wearer may be coated or doused with a flammable liquid or
gel, such as a policemen or soldier hit with a Molotov cocktail or
other incendiary device.
[0098] The present invention may be embodied in other specific
forms without departing from its spirit or essential
characteristics. The described embodiments are to be considered in
all respects only as illustrative and not restrictive. The scope of
the invention is, therefore, indicated by the appended claims
rather than by the foregoing description. All changes which come
within the meaning and range of equivalency of the claims are to be
embraced within their scope.
* * * * *