Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1260449
29,732
IMPROVED WARP KNIT FABRI~ CONTAINING WEFT
INSERTED ACTIVATED CARBON YARN
Field
This invention relates to warp knit fabrics
which contain activated carbon yarn.
,. ~ r ~
Background
U.S. 4,067,210 discloses warp knit fabrics made
of activated carbon yarn. The activated carbon yarn is
protected by being braided or wrapped with a protective
yarn which forms a covering over the carbon yarn. The
protective yarn covered activated carbon yarn is incorpo-
rated as the weft in a warp knit fabric by a weft inser-
tion procedure. According to this patent, the resultingwarp knit fabrics are permeable to air, possess good
stretchability because of the warp knit construction, are
quite strong and durable, and have excellent sorptive
power for toxic chemical vapors.
However, covering the carbon yarn with a second
yarn, as disclosed, for example, in U.S. 4,067,210, sub-
stantially adds to the fabric weight, provides a leakage
path between the carbon yarns and, in the case of cloth-
ing, the relatively straight lay of the weft inserted
covered carbon is too stiff for comfort. The stiffness in
the weft direction also contributes to carbon fiber damage
by abrasion.
U.S. 4,217,386 disclosed a laminated active
carbon fabric. The fabric is permeable to moisture vapor
and resistant to sweat penetration and poisoning, while
sorbing quantities of toxic chemical vapors. The lami-
.... ..... .
lZ604~
6110g-7~48
nated structure is multilayered, usually five-layered. The
structure comprises an inner woven ~abric made of yarns of active
carbon, two outer layers (webs) of spunbonded non-woven fabric,
and two intermedlate layers (mats), one on each side of the active
carbon fabric, each overlain by one of the outer layers of
spunbonded non-woven fabric.
United States 3,850,785 discloses a rein~orced,
activated carbon, fabric. The fabric is constructed by laminating
an activated carbon fabric having poGr textile properties to at
least one other fabric having good textile properties and bonding
the fabrlcs together by means of a hot-melt adhesive netting.
United States, 3,769,144 discloses a quilted fabric con-
talnlng hlgh surface area carbon flbers. The fabric comprises in
comblnatlon~ (1) at least one central layer of flexible carbon
fibers; (2) a pair of outerlayers of reinforcing fabric,
positioned on each side of the flexible carbon fiber layer; and
~3) a network of qullting stltchlng uniting the central and outer
layers into an integral quilted fabrlc.
United States 4,217,386, United States 3,850,787 and
United States 3,769,144 above relate to multilayer fabrlcs which
substantially increase the weight of the fabric. This increased
weight adds to increased heat retention. Another problem
a~sociated with these multilayers ls poor elastic property which
contributes to poor wear resistance and to user fatigue in the
ca~e of clothing.
A welcome contribution to the art would be a fabric
comprlsing activated carbon yarn that has improved elastlcity,
B
126044~
61109-7448
wear resistance and sorption of toxic chemical vapors, and is
lighter in welght. Such a contribution is provlded for by this
invention.
Summarv of the Invention
The present invention provides an improved knitted
activated carbon fabric comprising " a) a weft of a multl-fold
activated carbon yarn, said activated carbon yarn be1ng produced
by intertwinlng a plurallty of carbon contalnlng yarns together to
produce a multi-fold yarn and then ~ubjecting said multi-fold yarn
to an actlvatlon proces~; and (b) a warp of a hydrophobic mono-
filament yarn.
The preferred embodiments of the monofilament is a
polyester or a polyester and cotton blend, especially a 50/50
polyester/cotton blend.
In another embodiment, a hydrophilic layer is
incorporated on one slde of the above de6cribed warp knitted
actlvated carbon fabric.
The fabrics of thls inventlon may be used in clothing or
fabrlc enclosures--e.g., tents, wlndow covers, and the llke--to
protect indlvlduals from toxlc chemlcal vapors. The invention may
al~o be used a~ air fllters and in water treatment a6 well as
other appllcatlons regulrlng the filtration of toxic chemical
vapors, gase~ and liguids.
The term "twist coefficient~ refers to the primary yarn
~- and as used hereln means the.
Twlst Number Per Meter
Metrlc Count Of Spun Yarn
'' '
B
~,.
, ...........
1260449
61109-7448
The term "twist ratio" as used herein mean~ the ratio of
the twlst (final twist) of the activated carbon yarn to the twist
of the prlmary yarns.
The term "primary yarn" as used herein refers to the
individual plie~ of the multi-fold yarn.
~rlef Descri~tion of the Drawinqs
Figure 1 is a polnt diagram for a tricot or rasehel type
warp knlt fabric as deicribed in Example I.
Figure 2 i~ a point diagram for a tricot or raschel type
warp knit fabric with a backing layer incorporated into the
fabrlc.
Detalled DescriPtlon of the Invention
The drawing will be understood by those skilled in the
art without further detalled descriptlon thereof.
Thls inventlon provides an improved warp knltted
aetlvated earbon fabrle eomprlslng a weft of a multl-fold
aetlvated carbon yarn and a warp of a hydrophoble polymerlc mono-
filament yarn wherein every eour~e of sald aetlvated yarn 18
ln~erted aeross the full wldth of sald fabrie wlth said mono-
filament being ln the wales and cour~es of sald fabric.
The aetivated earbon fabries of this invention, as those~killed in the art can appreeiate, ean be produeed by a varlety of
knlttlng designs known in the art e.g., trieot or rasehel knlt
l fabrie deslgn.
7~ ~ A trleot knlt fabrle of thls invention has a deslgn
pattern repre~ented by the bar movement pattern.
front gulde bar~ 1-0, 0-1
-
J
', ' ' ' '" ''
~, .:, . ' ~' ' ' . ''". : , ,,
: ' ' '
" ~' ' : '. '
'~: ' , . :
'", ' ' ~' , ~ "
iZ~;OA49
61109-7g48
back guide bar: 1-0, 1-2
A raschel knit fabric having a design represented by the
bar movement pattern:
front guide bar: l-o, 0-1
back guide bar: 1-0, 1-2
may also be used to weave (knit) the fabrics of this invention.
A third beam may be added having the design pattern 9-0,
2-2 to incorporate a hydrophilic yarn or fibers as a layer on one
slde.
Suitable multi-fold activated carbon yarn utilized in
thi~ invention comprises a plurality of carbon containing
precursor yarns, intertwined together to produce a multi-fold yarn
and then subjected to an activation process.
Usùally the actlvated carbon yarns comprise a plurality
of carbon containing precursor yarns, intertwined together to
produce a multi-fold yarn and then sub~ected to an activation
process, said actlvated yarn having a tenacity of greater than
about 0.1 gram/denler (g/d) wlth about 1.0 g/d to about 4 g/d
being preferred and a carbon tetrachloride ~CC14) sorptivity of
greater than about 25% by weight, based on the weight of activated
carbon yarn, with about 25% to about 140~ being preferred.
Preferably the activated carbon yarns comprise a
plurality of oxidized yarns, intertwined together to produce a
multi-fold yarn and then subjected to an activation process, said
activated carbon yarn having a tenacity greater than about 1 (g/d)
and a CC14 sorptivity of greater than about 60~ by weight based on
the weight of activated carbon yarn. Preferably, the oxidized yarn is
4a
~' .
.
126~)44~9
an oxidized acrylic yarn.
The activated carbon yarns comprising a plur-
ality of carbon containing precursor yarns, preferably
oxidized acrylic yarns, or a combination of different
carbon containing precursor yarns are brought together and
arranged spatially by intertwining to form a multi-fold
yarn structure. Intertwining is defined as including any
method for making yarns including the art recognized
methods for making yarns from staple or continuous fila-
ments--e.g., twisting or braiding. Methods for making
yarns and the configurations by which yarns are made--
e.g., braided or twisted--are well known in the art.
Preferably, the multi-fold yarn for the activation process
is made by longitudinally twisting or braiding together a
plurality of carbon containing precursor yarns. The car-
bon containing precursor yarns generally have a twist
coefficient greater than about 65 and usually within the
range of from about 65 to about 150. The multi-fold yarn
made by twisting generally has from about 0.5 to about
10 turns per inch. The twist ratio is generally within
the range of from about 0.1 to about 0.5.
The multi-fold ya~n is generally made from about
2 to about 20 carbon containing yarns, preferably oxidized
acrylic yarns, with about 3 to about 10 being preferred.
The yarns can be intertwined together at one time or a
given number of yarns can be intertwined together to form
a unit and then a given number of units can be intertwined
together to form the multi-fold yarn for activation. For
example, 2 oxidized acrylic yarns can be intertwined to
form a pair and then 3 pairs can be intertwined to form
the multi-fold yarn for activation.
Those skilled in the art will appreciate that `
the denier of the individual plies and consequently the
denier of the plied yarn are generally chosen to meet
specific requirements of the end product.
Carbon containing yarns comprising one of the
following precursors may prove useful in producing the
,,
i260449
- 6 - 611~9-7448
activated carbon yarns utilized in this invention; phenolic,
poly(benzimidazole), poly(p-phenyleneterephthalamide), polyacrylo-
nitrile, pitch (petroleum or coal tar), and the like.
Examples of commercially available yarns are: KYNOL*,
a trade mark for a phenolic-aldehyde yarn available from American
Kynol, Inc.; KEVLAR ~ 49, brand of aramid yarn from E. I. du Pont
de Nemours ~ Co., Inc.; PYRON ~ brand of oxidized polyacrylonitrile
yarn from Stackpole Fibers Co., Inc.; CELIOX ~ brand of oxidized
polyacrylonitrile yarn from Celanese Corporation, Celion Fiber
Division; GRAFIL 'O'*, a trade mark for an oxidized polyacrylo-
nitrile yarn from Hysol Grafil Limited; FORTAFIL ~ OPF brand of
oxidized polyacrylonitrile yarn from Great Lakes Carbon Corp.
Of these yarns, oxidized acrylic yarns are widely used
with acrylonitrile oxidized yarns being preferred. A preferred
oxidized acrylonitrile based acrylic yarn is available from
Celanese Corporation, Celion Carbon Fiber Division under the trade-
mar CELIOX ~ . I
The multi-fold yarns are then subjected to an activation
process. The multi-fold activated carbon yarns are described else-
where.
Without wishing to be bound by theory, it is believed
that the leakage encountered with prior art fabrics is at least
partially due to a "wicking effect". Since the protective yarn is,
for example, wrapped or braided along the entire length of the
activated carbon yarn a leakage path is established from outside to
inside by a "wicking effect" when, for example, the fabric gets
12fiO44~
- 6a - 61109-7448
wet. This wicking effect is o~ercome by the use in this invention
of a hydrophobic monofilament yarn as the warp. The monofilament
yarns suitable for use include for example: polyesters such as
DENIER 20/1 SEMIDOLL MONOFIL available from Hanover Mills Inc.,
NY, NY.
,~
,. ..
'
,
~X60Af~
The monofilament generally has a denier of about
10 to about 100, with about 10 to about 30 being preferred
and about 15 to about 20 being most preferred.
The warp knit fabrics of this invention have
monofilament yarn in the warp while activated carbon yarn
is weft inserted a selected number of courses per inch-
i.e., from about 20 to about 60 courses per inch with
about 24 to about 50 being preferred and about 30 to about
40 being most preferred--to provide a warp knit fabric
which is flexible and has high sorptive capacity for toxic
chemical vapors and gases and liquids, is reasonably
strong, and has sufficiently good abrasion resistance to
retain a large amount of sorptivity for toxic chemical
vapors even after being subjected to considerable
abrasion. The warp knit fabrics may be produced on tricot
type or raschel type warp knitting machines modified so as
to insert the unprotected activated carbon yarn as weft
while the monofilament yarn is being warp knitted. Such
apparatuses and methods are exemplified by U.S. Patent No.
3,364,701 and U.S. Patent No. 3,495,423.
Although the activated carbon yarn utilized has
excellent tenacity, flexibility and abrasion resistance,
during experimental testing in a commercial weaving
process, it occasionally snags and is subject to a minimal
amount of breakage around sharp angle bends in the commer-
cial weaving equipment. It is to be noted that the break-
age which occurs with these multi-fold activated carbon
yarns is much less than that which occurs with other
activated carbon yarns. To overcome this, the knitting
3C equipment may be modified, for example, by placing plastic
sleeves at sharp angle bends to guide the yarn through.
It is preferred for the purposes of the invention
that the warp knit fabric contain at least 2 oz/yd2 of
the activated carbon yarn with about 3 oz/yd2 to about 7
oz/yd2 being most preferred. It is also preferred that
the warp knit fabric have an air permeability of at least
50 cubic feet/minute/square foot of fabric with about 200
lZ60A49
- 8 - 61109-7448
ft3/min/ft2 to about 1000 ft3/min/ft2 being most preferred.
Clothing constructed of warp knit fabric having the above-stated
preferred characteristics will be effective for protecting the
wearer of such clothing against toxic chemical vapors or gases for
a reasonable length of time, depending on the concentration of
such vapors or gases in the atmosphere, and may be worn without
experiencing undue heat stress since the fabric breathes while
sorbing the toxic chemical vapors or gases and is relatively light
weight due to the absence of multilayers and excessive support
yarns to protect the activated carbon yarn.
In another embodiment of this invention a layer of
hydrophilic fiber is incorporated on to one side of the warp knit
fabric described above. This can be done by known knitting
methods as for example, in the manner described in Figure 2 by,
for example, the addition of a third beam to a knitting machine of
the Karl Mayer type. When the added layer is placed toward the
skin of the wearer it improves abrasion resistance, protects the
wearer against carbon fiber cut ends and serves to spread
perspiration for easy release through to the outside of the fabric
Since this added layer is on one side only and does not penetrate
the activated carbon yarn layer, it does not produce a leakage
path for toxic liquid agents.
Hydrophilic fibers or yarns which are useful include but
are not limited to: 50/50 polyester/cotton (polycotton), 100%
cotton, 100~ polyester, rayon, wool, and linen.
~ The hydrophilic yarns have a denier of about 100 to
i~ X
:,. .. ,,:
~: .. . .
.
. .
'' ~ , ., ', ` :- r
~ ':' ` ' .. :
'~,`'~ ` ' '' ~'`"
~Z6044<.3
- 8a - 61109-7448
about 300 with about 150 to about 250 being preferred and about
175 to about 190 being most preferred. It is anticipated that the
addition of the second layer will add only about 1 to about 1.5
oz/yd2 to the weight of the warp knitted fabric described above.
':
,~ .
~260A49
- 9 - ~110~-7~48
Wh;le the invention has been described in terms of
warp ~nit fabrics produced with weft insertion of activated carbon
yarn to provide toxic vapor sorptive capacity to the fabrics, it is
to be understood that similar results may be obtained employing
weft knitting machines in which warp yarns of activated carbon
yarn are inserted and held in place in the fabric by the knit weft
monofilament yarn.
The following examples are provided for the purposes
of illùstration only and should not be considered as limiting the
invention in any way. It is to be understood that variations of
the invention are possible which do not depart from the spirit or
scope of the appended claims.
EXAMPLE I
Tricot Warp Knit Activated Carbon Fabric
A six-ply CELIOX ~ oxidized stabilized yarn having a
worsted count of 6/10 was activated using the single furnace
technique. The multi-fold yarn had a twist coefficient of about
87.5 and a twist ratio of about 0.2. The activated carbon yarn has
a tenacity of 1.3 g/d, weight 1300 denier and static sorption to
CC14 greater than 80% by weight, based on the weight of the
activated carbon yarn. The yarn was knitted into fabric using a
Karl Mayer Weftamatic Warp Knit Machine and a 2 bar chain stitch
plus tricot. Monofilament polyester of 20 denier was machine fed
in the warp while the activated carbon yarn was fed in the weft.
Testing yielded the following characteristics:
i2604~
- 1 o -
Weight 3.75 oz/yd2
Thickness O.OlS inch
Active Carbon Content 81%
- Static Sorption 70%
Dynamic Sorption 2.15 mg/cm2 (CC14)
Porosity ,~ 975 ft3/min/ft2
Static and Dynamic s-orption of CC14 was tested
according to the standard method for ~ilitary Clothing
Material.
Static CC14 sorption by weight gain in saturated
vapor of CC14 for 4 hours minimum was 70~/O.
Dynamic sorption testing using the standard 5
mg/L CC14 threat.~oncentration in nitrogen at 1 L/min .e -
rate through 100 cm sample cup area to a downstream limit
of 0.5 mg/L resulted in 43 minutes test time to the end
point (2.15 mg/cm2),
This data is significantly better than the
requirements of a U.S. specified military laminate for
chemical protection which describes a carbon powder
loaded polyurethane ~oam system. MIL-C-43858 (GL) lists
the following requirPments:l
Weight 7.0-9.5 oz/yd2
Thickness 0.070-0.110 inch
Dynamic Sorption 1.8 mg/cm2 (minimum CC14)
Porosity 40 ft3/min/ft2
It is anticipated that when the fabric exemplified
by this Lxample is laminated to a "body side" fabric, the
overall laminate weight will be under about 5.5 oz/yd2.
This is a significant reduction in weight compared to
existing prior art fabrics.
~260449
A tensile test of this fabric using a TMI
tensile tester gave the following results:
Tensile strength in the activated
carbon yarn weft direction......... 92 lbs/in
S Tensile strength in the polyester
monofilament warp direction........ 12 ibs/in
This data demonstrates satisfactory strength
for clothing applications.
_~ r ~~ ~ -
:
:
.~
