CA2014249C - Low permeability fabric and method for making same - Google Patents
Low permeability fabric and method for making sameInfo
- Publication number
- CA2014249C CA2014249C CA002014249A CA2014249A CA2014249C CA 2014249 C CA2014249 C CA 2014249C CA 002014249 A CA002014249 A CA 002014249A CA 2014249 A CA2014249 A CA 2014249A CA 2014249 C CA2014249 C CA 2014249C
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- permeability
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- inch
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Abstract
A strong, lightweight, thin, flexible fabric of low permeability comprising an uncoated woven cloth characterized by a permeability of not more than one cubic foot of air per minute per square foot of cloth (0.5 cm3/sec/cm2 ) at a pressure drop of 0.5 inch of water (1.27 cm) across the cloth. The cloth is calendered on both sides to reduce its permeability.
Description
~ l 201~249 a332r 092,089 ~, .
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., LOW PERMEABILITY FABRIC
AND MET~OD OF MAKING SAME
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- The present invention eelates to a fabric of - low permeability suitable for use in an air bag and, more particularly, to such a fabric formed of an uncoated woven cloth.
;~ 5Low permeabilitv fabrics have a multitude of potential uses, e.g., air-filled or water-filled mattresses, sleeping bags, pi1lows, life belts, life boats, chairs, ottomans, etc. Each of these alternative uses may have a different maximum 10permeability requirement.
Among the most demanding and critical of this multitude of potential uses is their employment in eYpansible passenger restraint bags for automobiles ("air bagsn). The air bags are adapted to be 15inflated instantaneously with hiqh pressure qas in the event of a collision to prevent the movement of the occupant for safety reasons. For this purpose, the air bag is qenerally made of an air-impermeable material and formed with an opening ~rom which the 20high pressure gas introduced into the bag is exhausted, whereby the enerav resulting from the *
.
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201~249 occupant's strikinq against the bag upon a collision . .
and the energy of the subsequent pressing movement are absorbed to reduce the impact. This potentially life-saving use requires that the fabric exhibit not onlv low permeability, but also be strong, lightweight, thin and flexible so that it can be ; easily and compactlY folded into its appropriate :-- , storage container ready for use, withstand the - stronq shock occurring when it is initiallY
deployed, and add as little weight as possible to the person or vehicle transporting it.
~:, :
-~ In the past, fabrics intended for use in air .... .
bags have been made from a wide variety of materials including macromolecular film (such as polyethylene) and inorganic fibers (such as glass fiber).
; Such patents as U.S. 3,705,645 and U.S.
- ~ 3,892,425 illustrate the conventional manner of forming such fabrics from a woven cloth by coating - the cloth with a resin binder to reduce its permeability. Low permeability fabrics for use in ::
air bags are conventionally made of nylon or polyester which has been coated with neoprene, ~; urethane, or silicon resin, even though the coating recessarily increases the weight, thickness (bulk), stiffness, and cost of the cloth while reducinq its flexibilitv, tear strength, over-all strength (due .
201~249 to prolonged exposure to heat durinq the coatina operation) and shelf-life (as the coatings tend to deq,rade over time). Variations in the coating thickness from lot to lot or within a sinale ]ot can also introduce undesirable permeabilitY fluctuations for a given piece of fabric.
U.S. 3,730,551 discloses a knit or woven nylon or polyester material suitable for use in an air bag, but there is no specific disclosure of the permeability of the fabric or precisely how the fabric is woven (or coated) to provide a suitable permeability according to 1971 standards.
In any case, air bag manufacturers have recently proposed a new and extremely rigorous requirement of low permeability for an uncoated .
fabric not exceedinq one cubic foot of air per minute per s~uare foot of cloth (O.S
cm7/sec/cm2) at a pressure drop of O.S inch of water (1.27 cm) across the cloth (i.e., 1 CFM). In addition, an air hag fabric should be flexible, thin, preferably with a thickness of less than 0.016 inch (0.041 cm), lightweiqht, preferably with a ~ weiqht of not more than 8.25 oz/scuare yard (280 qms/m2), and stronq, preferably with a strength characterized by a tensile strength of at least 300 lbs (1334 newtons), a Mullen burst strength of at "' , .
201~9 least 650 psi (4482 kilopascals), and a trapezoid tear of at least 4n lhs. (178 newtons). Preferably the fabric should also be flexible, compactable, have an elongation at break of at least 25~, and exhibit a storage or shelf life of 5 to 10 years without substantial deterioration.
A strong, lightweight, thin, flexible fabric has been sold for use in bomb parachutes as a bomb parachute (for the controlled descent of a bomb, , 10 rather a person), but this fabric was characterized by a permeability of about 1.5-2.0 CFM
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(specification maximum 3.0 CFM) and thus would not - meet the aforenoted extremely low permeability requirement of the proposed new standard for an air bag fabric. Further, the fabric, made of an uncoated, woven nylon calendered on one side to reduce permeabilitv (210/34/0 multifilament yarn woven in a 1 X 2 modified Oxford weave, 80 ends/inch X 80 picks/inch), exhibited low flexibilitY and hence poor compactability.
Thus, the need remains for a fabric which is strong, lightweiqht, thin and flexibile, yet of extremely low permeability.
Accordingly, it is an obiect of the present invention tn provide a strong, liqhtweiqht, thin, flexible fabric havinc a permeability of not more than l CFM.
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Another object is to provide such a fabric which is suitable for use in air bags.
A further obiect is to provide a method of makinq such a fabric or a similar one having a permeahility of not more than 3 CFM.
It has now been found that the above and related obiects of the present invention are obtained in a strong, lightweight, thin, flexible ; fabric of low permeability comprising an uncoated ;
-~ 10 woven cloth characterized by a permeability of not more than one cubic foot of air Der minute per sauare foot of cloth (0.5 cm3/sec/cm2) at a pressure drop of O.S inch of water (1.27 cm) across the cloth (i.e., 1 CFM). Preferably the fabric is further characterized by a Mullen burst strenqth of at least 650 psi (4482 kilopascals), a tensile ::
~trenqth of at least 300 lbs. ~1334 newtons), a . . :
trapezoid tear of at least 40 lbs. (178 newtons), an -~ elonaation at break of at least 25~, a weight of not more than 8.25 oz/sauare yard (280 qm/m2), and a thickness of less than Q.016 inch (0.041 cm).
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In a preferred embodiment, the cloth is Dolyester and woven in a plain or basket weave, preferably a 1 X 1 plain or 2 X 2 basket weave. The cloth is woven about 51-52 ends/inch by about 43-52 picks/inch (20 ends/cm by 17-20.5 picks/cm). The :~:
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~ 2014249 cloth is woven of not qreater than 600 denier multifilament ~arn, oreferably 400-600 denier - multifilament Yarn, havina 100-300 filaments.
The low permeability is achieved by calenderina the cloth on both sides.
~ The invention also encompasses a method of making such a fabric bv providing an uncoated, oven, strong, liahtweiaht, thin, flexible cloth of ::
high permeability. Then the cloth is calendered on both sides to reduce the permeability to not more than 3 CFM, preferably to not more than 1 CFM.
In a preferred embodiment the cloth is calendered in a calender exertinq a pressure of 65-75 psi (448-517 kilopascals) at a temperature of about 350-370 F (177-188 C), preferably a calender exerting a pressure of 70 Dsi (483 kilopascals) at a temperature of about 360F
- (182C). Thus the cloth may be calendered in a calender exerting 65-80 tons/70 inch base (59.0-72.6 :~ .
X 106 gm/178 cm~ at a nominal nip of 0.5 inch (1.27 cm) at a temperature of 350-370F
(177-188C~, preferably a calender exerting about 70 tons (63.5 X 103 kilograms) at a temperature of :, :
about 360 F (182 C~.
The invention further encompasses the fahric oroduced by the method.
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-- 20142~9 The ahove brief description, as well as further obiects and features of the cresent invention, will be more fullv understood bv reference to the followinq detailed description of the presently preferred, albeit illustrative, embodiments of the present invention when taken in coniunction with the accompanyinq drawing wherein:
FIG. 1 is a schematic view of the cloth ~assing through a calender which calenders both sides of the cloth, accordina to the method of the Present invention.
One aspect of the present invention comprises a strong, lightweight, thin, ~lexible fabric of low permeability comprisinq an uncoated woven cloth characterized by a permeability of not more than one cubic foot of air per minute per sauare foot ~f cloth (0.5 cm /sec/cm ) at a pressure drop of 0.5 inch of water (1.27 cm) across the cloth (hereinafter CFM).
:;: : 20 The level of low permeability required in the fabric will vary according to the reauirement of a particular manufacturer for a aiven application. In the past it has been exceedinqly difficult to reliably and consistently obtain ].ow permeabilitv in uncoated fabrics and, accordingly, a permeability of 3 CFM or less has ~een considered to be "zero"
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20142~9 permeabilitv and sufficient to meet the most `~ ~ stringent of air baq manufacturer's requirements.
On the other hand, the proposed new standards for uncoated air bag fabrics reauire a permeabilitv of ~ 5 not more than I CFM, a standard which must he met .~ uniformly and consistently both throughout a batch and from batch to batch over time.
The strength of the fabric is a composite of its Mullen burst strenqth, its tensile strenath and its trapezoid tear strenath. More particularly, its Mullen burst strenqth is at least 650 psi (4482 kilopascals), its tensi]e strength is at least 300 lbs. (1334 newtons), and its trapezoid tear strength is at least 40 lbs. (178 newtons). Preferably its elongation at break is at ]east 25%. The high strenqth characteristic of the fabric is an essential characteristic of a fabric intended for use in an air baa where the air bag must be able to :.
withstand the initial shock of an explosive inflation and immediately thereafter the imPact of someone hittinq it as the passengers are thrown forward. It must withstand these forces without burstina, tearing or stretchinq to the point where - the air bag no lonqer serves its protective function~
~o be suitable for use in air bags, the fabric ~ must also be lightweight, thin and flexible as the :'- , .~
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~ 4 air baq formed of the fabric must he capable of ~; being folded and compacted so as to fit within an extremely limited volume, such as that available within the steerina column or about the already crowded dashboard panel adiacent the driver. As a practical matter, the fabric must also be liqhtweiqht so that the air haq does not contribute unnecessarily to the weiaht of the car, ~hereby reducinq mileage. Thus the weiqht of the fabric is not more than 8.25 ounces per sauare yard (280 qm/m ), and the thickness is less than 0.016 inch (0.041 cm).
The properties of the fabric discussed herein are determined by Federal ~est Method Standard No.
191A and, in Particular, for permeability ~ethod 5450, for hurst strenqth Method 5122, for tensile strenath and elonaation, Method 5]00 Grah, for tear ,, .
strenqth Method 5136, for weiqht Method 504], and Eor thickness ~ethod 5030.
Accordinc to the present invention, ~he fabric is preferably formed of nylon or polyester yarn, with polYester yarn being preferred over nylon yarn for reasons unique to the present invention as will be explained hereinafter. Other thermoplastic yarn may be used for ~articular applications.
The cloth is woven of multifilament yarn not . :
~ qreater than 600 denier, and preferably 400-600 ~ ~ , i:: -. .
. :~.
~- 2014249 ,: 1 o denier, 100-300 filaments ~er yarn bundle. Lower denier yarns provide liqhtness and thinness, but ~` afford less strength and are more expensive as more yarn and more weavinq is reauired to provide the same coveraqe. Uigher denier yarn tends to produce : i a heavier and thicker fabric which is harder to fold and makes control of the oermeabilitY during the manufacturing process difficult, especially during the manufacturing process of the present invention as will be explained hereinafter. More particularly, the warp yarn is preferably 440/100/3 1/4 Z (that is, 440 denier, 100 filaments per yarn bundle, 3 1/4 turns per inch of yarn with a counter-clockwise twist), and the fill yarn is - lS preferably 440/100/0 (that is, 440 denier, 100 filaments per varn bundle, with a zero or "producer's" twist). A minimum of 100 filaments per yarn bundle is preferred.
In order to enhance the flexibility of the woven cloth, the cloth is woven in a basket weave, referably a 2 X 2 basket weave. It will be appreciated that the use of a basket weave, and in particular a 2 X 2 basket weave, increases the ~ermeability of the cloth. Nonetheless, the Drocessing of the cloth according to the present ~ :
invention so decreases its permeabilitY as to enable use of the 2 X 2 basket weave while still enablinq ~ .
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-?'~- 201~2~9 .. --~,,, the cloth to meet the low ~ermeabilitY requirement.
As the forces exerted on the fabric may be in anv direction, it is preferred to use a weave which provides a balanced strength extenàing in all :
directions, such as a basket weave (as oPposed to an Oxford weave). Other weaves may be employed instead of a basket weave -- e.a., a 1 X 1 Plain weave. A 1 .~, X 1 plain weave is naturally tighter than a 2 X 2 basket weave and thus provides an even lower ~~ 10 permleability. Furthermore, the seam slippage is ^ decreased so that there is less windowing or opening of the seam during inflation, thereby improving the dynamic permeability of the fabric. While the 1 X 1 .~ .
Plain weave is naturally stiffer than a 2 X 2 basket weave, it has been found to be thinner by about 20%. The increased thinness compensates for the increased tiahtness so that the two weaves afford genera]ly comparable compactability.
The cloth is preferably woven, for a 2 X 2 hasket weave, about 52 ends/inch (20.5 ends/cm) and ~2 picks/inch (20.5 picks/cm) to provide a desirable tightness of the weave, althouqh qreater and fewer picks and ends per inch may be used. (About 51 ends/inch and 43 picks/inch are suitable for a 1 X 1 :: , .
~ ~ 25 rlain weave.) The optimum end and Pick count will ::~.,-depend to a large dearee upon the thickness (i.e., denier) of the yarn. For thick 600 denier yarn, the , , ~' -: .:
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end and pick count may be as much as 33~ less. For thin 40n denier yarn, a variation of + 5~ in end and pick count is acceptable. The tiqhter the weave (that is, the higher the end and pick count~ the less ~ermeable the cloth on the other hand, the looser the weave (that is, the lower the end and pick count), the less expensive the cloth in terms of both yarn material and weavinq costs).
- The desired low permeability of the fabric of the present invention is achieved by calenderinq the ~: .:
uncoated woven cloth on both sides thereof to reduce its permeability while at the same time retaininq its desirable characteristics of high strength, liqhtweiqht, thinness, and flexibility. While the .
calendering operation will be discussed hereinbelow in terms of reducinq the permeabilitY to not more than 1 CFM, clearly the parameters of the same calendering o~eration can be adiusted to provide a fabric having any permeability of not more than 3 C~M. It is believed that the calendering operation replasticizes the thermoplastic material of the :i woven cloth and sauashes and flattens the high ; points on both sides of the fabric to block the ,: .
- permeability-providing interstices. The calenderinq ~r~ 25 operation Produces a glossy sheen on the calendered -;h - I side of the fabric, so that a fabric which has been calendered on both sides is easily distinguishable ., ~ .
~ 2014249 i/
from uncalendered fabric or fahric which has been calendered on onlv one side.
Calenderina of the cloth on both sides thereof may be performed in a number of different ways de~endinq on such factors as the number of available existina calenders, the willinqness to create ~ specialized calenderina eauipment, the desirability - of continuous ~ersus batch ooeration, and the like.
As in a standard calenderinq operation, prior to . 10 calendering the cloth is typically scoured to clean \ the same (with detercent, anti-bacterial or anti~-fungal ingredients, dyes and other conventional materials added, as desired), and then dried and -~ heat set in a tenter oven (for example, at 250F). In order to exert pressure on the cloth as it passes through the calender, the cloth is insulated from the pressure roll (typicallY made of steel~ by a cushioninq roll (typical]y a steel roll havinq a number of coaxial disks of cotton paper thereabout). ~he hot roll (typically made of steel) on the other side of the cloth is heated to about : :~
350-370 F, for example, by hot oil flowinq ~ therethrough. In order to perform the second :.
calenderina operation -- that is, the calendering of the opposite side of the cloth -- in a hatch orocess, .he cloth may be inverted (to exchanqe sides) and passed through the same calendar a second '"
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: 2014249 time. Alternatively, in a continuous process, the cloth mav be oassed through an inverted second calender -- that is, a calender having the pressure and cushioning roll combination interchanged with the hot roll.
Referrina now to the drawinq, therein illustrated is a continuous process for the ::
calenderinc of cloth on both sides according to the ;::
present invention. The scoured and dried cloth 10 emeraing from a tenter oven (not shown) passes throuqh a conventional calender qenerally designated C including a pressure roll 12 bearing upwardly on a cush~oning roll 14 in turn bearing upwardly on the ;., ; bottom cloth surface, with a hot roll 16 bearinq downwardly on the upper cloth surface. Subseauently the cloth ]0, now calendered on the bottom surface, passes through an inverted calender generally designated C' includinq a pressure roll 12' bearing downwardly on a cushioning roll 14' in turn bearing downwardlv on the upper cloth surface, with a hot roll 16' bearing upwardly on the bottom cloth surface. The resultant cloth is calendered on both -:
- its top and bottom surfaces.
It will be appreciated that the two calenderina operations can he ~erformed usina a sinqle modified - calendar havina, for example, a cushionina roll and a hot pressure roll on each side of the cushionina ::;
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20142~9 ,:
roll. The cloth would pass initially hetween the cushionin~ roll and the ~irst hot ?ressure roll and then, after being ~wisted so that the calendered cloth surface which was adiacent the cushioninq roll ~` 5 is now remote from ~he cushioning roll, loop back between the cushioninq roll and the second hot pressure roll.
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Preferably the calenders exert a pressure of ~ .
65-75 psi (448-517 kilopascals) at a temperature of 350-370 F (177-188C1. A pressure of about 70 psi (483 kilopascals) and a temperature of about 360F (182) are preferred. Typically higher pressures are utilized in connection with lower temperatures, and lower pressures are utilized in conjunction with hiqher ~emDeratures. For exam~le, the calender maY exert a pressure of 65-80 tons per 70 inches of base (59.0-72.6 X 103 kiloqrams for a 178 cm base) at a nominal nip of 0.5 inch (1.27 cm), preferably about 70 tons (63.5 X 103 kilograms).
Where substantiallY hiqher calenderinq pressures are utilized, the low permeability is obtained onlv at the cost of the strength of the fabric which in effect becomes a plain sheet of plastic lackinq the strenqth of a woven. Where the :: .
calenderinq pressure is substantiallY lower, the calenderinq operation fails to squash and flatten : ' ~:
.
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- the high spots of the cloth as necessary to achieve :::
low permeability.
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,~s each calenderina o~eration subiects the cloth to an elevated temperature for only a short duration (e.q., approximately one second), the cloth is not thermally degraded as it is during a coatina operation, where the exposure of the cloth to an elevated temperature is prolonaed.
- - It is theorized that the calendering operation : :~ .
to a limited degree replasticizes the thermoplastic material of the woven cloth and mashes down the - hills or high spots of the woven cloth, thereby to :. .
close the adiacent interstices and so reduce the overa]l permeability of the cloth. Calendering on both sides of the cloth is essential as apparently ~~, ~ calenderinq on one side only does not effect :- .
blockage of each interstice (even when calendered twice on that side) while calendering on both sides) :-:, : :-~ substantially reduces and almost eliminates the :: : _ ~
~ 20 number of unblocked interstices. Alternativelv, it is possible that calendering on one side only, while - affecting substantially all interstices, fails to provide lO0~ blockinq of each interstice, and the calendering on the opposite side provides the additional blockaqe of each interstice necessary to substantially reduce the permeability of the cloth.
Indeed, the reason why it is preferred that the yarn '' , i:
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of the present invention have a denier not exceeding 600, and oreferablY not exceedina 500, is that higher denier yarns have nigh spots which are ::::
difficult to mash down.
The reason why polyester cloth is preferred over nylon cloth in the present invention is that polyester retains its low permeability over an extended period of time (such as the 5 to 10 years of life which may be required for an automobile air baq). It will be appreciated that in a conventional air baq fabric where reduced permeability is :
obtained by coatinq, nylon remains a preferred material for a variety of reasons including ease of coating. On the other hand, in the fabric of the prPsent invention where an uncoated fabric achieves - . low permeability through calenderinq, the polyester .
fabric affords enhanced lonaevitv. It is theorized that the superiority of polYester over nvlon for the purpose of the present invention arises out of its :':
lower moisture reqain properties. Both nvlon and -polyester are hydrophobic fibers, and both are ~- thorouqhly dried in the tenter oven prior to - ~ calenderina. Over a period of time after ~::: ,,.
~ calendering (during the S-l0 year anticioated :
-- 25 lifetime of the air baa), the nylon fabric will ~ exhibit a nigher moisture regain (about ~.5%) .:
~- relative to the polyester (about 0.4~). As the :~
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201424~
nylon fabric regains moisture, it also tends to resume its oriqinal woven configuration, with the one-time hills crushed bv the calendering o~eration into or over the interstices departing the interstices and resuming their prior orientation, thus allowinq a return to a higher permeability.
Further, while the nYlon fabric may initiallv exhibit a higher tensile strength (175-183 lbs.) than the polyester fabric (148 lbs.), after oven aging at 300F for ~8 hours the nylon fabric tensile strenqth degrades sharply (to 83-87 lbs.) while the polyester fabric tensile strenqth remains substantially constant (at 148 lbs.).
~ This followinq example illustrates the relative - 15 effects of calendering both sides of a fabric, - relative to calenderinq only one side of the fabric.
A test cloth had a warp of 440/100/3 1/4 Z yarn and a fill of 440/100/0 yarn. The cloth was a 2 X 2 basket weave.
Calendering was performed at a pressure of 70 ~-~ psi and 360 F for ~each run. One sample of the fabric was calendered twice on one side, and other sample of the fabric was calendered once on each side. Permeability of the fabric was measured u~ before any calenderina operation, after the Eirst calenderinq operation, and after the second '.~ :-: -, ~: :
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calenderinq operation. The resultamt permeabilities of the fabric samples are indicated in the Table.
TABLE
CalenderingCalenderinq Same Opposite Side, CFMSides, CFM
Before Calenderinq 24.20 22.90 After 1st Calendering 1.82 1.63 After 2nd Calendering 1.42 q.62 Thus, calendering on one side produced a verv :::
substantial lesseninq of permeability. While a second calenderinq on that one side afforded a ~ further small decrement in permeabilit~, a second .-~
calendering on the other side of the fabric produced a substantial decrease in permeability, one '; . 15 sufficient to reduce the permeability below the l .::::-CFM level. In other words, when calenderinq is -- performed on opposite sides of the fabric, ~he second calendering is more effective than when calendering is performed twice on the same side of the fabric. This is true both in terms of the absolute and relative decreases in permeability resulting from the second calenderinq operation. In absolute terms, the second calenderina operation (on the opposite side) produced a decrease in ~`- 25 permeability which was 2 l/2 times that Prod~ce~
when calenderinc was performed twice on the same ~ side; in relative terms (as a percentage of the :
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201~2~9 ` 20 !
~~, permeability remaining after the first calenderina :-, ~- operation), the decrease in permeability was almost . .,~ .
~ three times greater.
`~ After calenderinq on opposite sides, the cloth had 54 ends per inch and 51 picks per inch, and had ~. , .. ,__, ,- a Mullen burst strength of 905 psi, a tensile strength of 548-558 lbs., a trapezoid tear strength of 208-372 lbs., an elonqation at break of 38-50%, a weiqht of 7.22 oz./sauare yard and a thickness of 0.010 inch.
By way of comparison, a 1 X 1 plain polYester weave cloth of similar yarns had, after similar calendering on both sides, 51 ends per inch and 43 ::
picks per inch and had a permeability of 0.21 CFM.
: ~ .
` 15 The cloth had a Mullen burst strength of 825 psi, a :~ :
tensile strenqth of 494-552 lbs., a trapezoid tear , strength of 64-108 lbs., an elonqation at break of 36-37%, a weight of 6.29 oz./sauare yard and a :~ , thickness of 0.0078 inch.
:,:.
~ 20 To summarize, the present invention provides an - uncoated woven fabric which is stronq, lightweiqht, :: ~
thin and flexible, yet has an extremelY low permeability -- namely, a permeability not higher than 1 CFM -- so as to render it suitable for use in 25 air baas even accordinq to pro~osed new standards.
Now that the preferred embodiments of the :
present invention have been shown and described in ,, : ~
:
i ~3 detail, various modifications and improvements thereon will become readily a~parent to those - skilled in the art. Accordin~ly, the appended claims are to be construed broadly in a manner : S consistent with the spirit and scope of the invention herein.
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., LOW PERMEABILITY FABRIC
AND MET~OD OF MAKING SAME
. .
- The present invention eelates to a fabric of - low permeability suitable for use in an air bag and, more particularly, to such a fabric formed of an uncoated woven cloth.
;~ 5Low permeabilitv fabrics have a multitude of potential uses, e.g., air-filled or water-filled mattresses, sleeping bags, pi1lows, life belts, life boats, chairs, ottomans, etc. Each of these alternative uses may have a different maximum 10permeability requirement.
Among the most demanding and critical of this multitude of potential uses is their employment in eYpansible passenger restraint bags for automobiles ("air bagsn). The air bags are adapted to be 15inflated instantaneously with hiqh pressure qas in the event of a collision to prevent the movement of the occupant for safety reasons. For this purpose, the air bag is qenerally made of an air-impermeable material and formed with an opening ~rom which the 20high pressure gas introduced into the bag is exhausted, whereby the enerav resulting from the *
.
::
201~249 occupant's strikinq against the bag upon a collision . .
and the energy of the subsequent pressing movement are absorbed to reduce the impact. This potentially life-saving use requires that the fabric exhibit not onlv low permeability, but also be strong, lightweight, thin and flexible so that it can be ; easily and compactlY folded into its appropriate :-- , storage container ready for use, withstand the - stronq shock occurring when it is initiallY
deployed, and add as little weight as possible to the person or vehicle transporting it.
~:, :
-~ In the past, fabrics intended for use in air .... .
bags have been made from a wide variety of materials including macromolecular film (such as polyethylene) and inorganic fibers (such as glass fiber).
; Such patents as U.S. 3,705,645 and U.S.
- ~ 3,892,425 illustrate the conventional manner of forming such fabrics from a woven cloth by coating - the cloth with a resin binder to reduce its permeability. Low permeability fabrics for use in ::
air bags are conventionally made of nylon or polyester which has been coated with neoprene, ~; urethane, or silicon resin, even though the coating recessarily increases the weight, thickness (bulk), stiffness, and cost of the cloth while reducinq its flexibilitv, tear strength, over-all strength (due .
201~249 to prolonged exposure to heat durinq the coatina operation) and shelf-life (as the coatings tend to deq,rade over time). Variations in the coating thickness from lot to lot or within a sinale ]ot can also introduce undesirable permeabilitY fluctuations for a given piece of fabric.
U.S. 3,730,551 discloses a knit or woven nylon or polyester material suitable for use in an air bag, but there is no specific disclosure of the permeability of the fabric or precisely how the fabric is woven (or coated) to provide a suitable permeability according to 1971 standards.
In any case, air bag manufacturers have recently proposed a new and extremely rigorous requirement of low permeability for an uncoated .
fabric not exceedinq one cubic foot of air per minute per s~uare foot of cloth (O.S
cm7/sec/cm2) at a pressure drop of O.S inch of water (1.27 cm) across the cloth (i.e., 1 CFM). In addition, an air hag fabric should be flexible, thin, preferably with a thickness of less than 0.016 inch (0.041 cm), lightweiqht, preferably with a ~ weiqht of not more than 8.25 oz/scuare yard (280 qms/m2), and stronq, preferably with a strength characterized by a tensile strength of at least 300 lbs (1334 newtons), a Mullen burst strength of at "' , .
201~9 least 650 psi (4482 kilopascals), and a trapezoid tear of at least 4n lhs. (178 newtons). Preferably the fabric should also be flexible, compactable, have an elongation at break of at least 25~, and exhibit a storage or shelf life of 5 to 10 years without substantial deterioration.
A strong, lightweight, thin, flexible fabric has been sold for use in bomb parachutes as a bomb parachute (for the controlled descent of a bomb, , 10 rather a person), but this fabric was characterized by a permeability of about 1.5-2.0 CFM
-:,:
(specification maximum 3.0 CFM) and thus would not - meet the aforenoted extremely low permeability requirement of the proposed new standard for an air bag fabric. Further, the fabric, made of an uncoated, woven nylon calendered on one side to reduce permeabilitv (210/34/0 multifilament yarn woven in a 1 X 2 modified Oxford weave, 80 ends/inch X 80 picks/inch), exhibited low flexibilitY and hence poor compactability.
Thus, the need remains for a fabric which is strong, lightweiqht, thin and flexibile, yet of extremely low permeability.
Accordingly, it is an obiect of the present invention tn provide a strong, liqhtweiqht, thin, flexible fabric havinc a permeability of not more than l CFM.
~.
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201~4g :: s ;
Another object is to provide such a fabric which is suitable for use in air bags.
A further obiect is to provide a method of makinq such a fabric or a similar one having a permeahility of not more than 3 CFM.
It has now been found that the above and related obiects of the present invention are obtained in a strong, lightweight, thin, flexible ; fabric of low permeability comprising an uncoated ;
-~ 10 woven cloth characterized by a permeability of not more than one cubic foot of air Der minute per sauare foot of cloth (0.5 cm3/sec/cm2) at a pressure drop of O.S inch of water (1.27 cm) across the cloth (i.e., 1 CFM). Preferably the fabric is further characterized by a Mullen burst strenqth of at least 650 psi (4482 kilopascals), a tensile ::
~trenqth of at least 300 lbs. ~1334 newtons), a . . :
trapezoid tear of at least 40 lbs. (178 newtons), an -~ elonaation at break of at least 25~, a weight of not more than 8.25 oz/sauare yard (280 qm/m2), and a thickness of less than Q.016 inch (0.041 cm).
: ~ .
In a preferred embodiment, the cloth is Dolyester and woven in a plain or basket weave, preferably a 1 X 1 plain or 2 X 2 basket weave. The cloth is woven about 51-52 ends/inch by about 43-52 picks/inch (20 ends/cm by 17-20.5 picks/cm). The :~:
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~ 2014249 cloth is woven of not qreater than 600 denier multifilament ~arn, oreferably 400-600 denier - multifilament Yarn, havina 100-300 filaments.
The low permeability is achieved by calenderina the cloth on both sides.
~ The invention also encompasses a method of making such a fabric bv providing an uncoated, oven, strong, liahtweiaht, thin, flexible cloth of ::
high permeability. Then the cloth is calendered on both sides to reduce the permeability to not more than 3 CFM, preferably to not more than 1 CFM.
In a preferred embodiment the cloth is calendered in a calender exertinq a pressure of 65-75 psi (448-517 kilopascals) at a temperature of about 350-370 F (177-188 C), preferably a calender exerting a pressure of 70 Dsi (483 kilopascals) at a temperature of about 360F
- (182C). Thus the cloth may be calendered in a calender exerting 65-80 tons/70 inch base (59.0-72.6 :~ .
X 106 gm/178 cm~ at a nominal nip of 0.5 inch (1.27 cm) at a temperature of 350-370F
(177-188C~, preferably a calender exerting about 70 tons (63.5 X 103 kilograms) at a temperature of :, :
about 360 F (182 C~.
The invention further encompasses the fahric oroduced by the method.
~ , ' '.
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-- 20142~9 The ahove brief description, as well as further obiects and features of the cresent invention, will be more fullv understood bv reference to the followinq detailed description of the presently preferred, albeit illustrative, embodiments of the present invention when taken in coniunction with the accompanyinq drawing wherein:
FIG. 1 is a schematic view of the cloth ~assing through a calender which calenders both sides of the cloth, accordina to the method of the Present invention.
One aspect of the present invention comprises a strong, lightweight, thin, ~lexible fabric of low permeability comprisinq an uncoated woven cloth characterized by a permeability of not more than one cubic foot of air per minute per sauare foot ~f cloth (0.5 cm /sec/cm ) at a pressure drop of 0.5 inch of water (1.27 cm) across the cloth (hereinafter CFM).
:;: : 20 The level of low permeability required in the fabric will vary according to the reauirement of a particular manufacturer for a aiven application. In the past it has been exceedinqly difficult to reliably and consistently obtain ].ow permeabilitv in uncoated fabrics and, accordingly, a permeability of 3 CFM or less has ~een considered to be "zero"
, . ,, . . ~
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20142~9 permeabilitv and sufficient to meet the most `~ ~ stringent of air baq manufacturer's requirements.
On the other hand, the proposed new standards for uncoated air bag fabrics reauire a permeabilitv of ~ 5 not more than I CFM, a standard which must he met .~ uniformly and consistently both throughout a batch and from batch to batch over time.
The strength of the fabric is a composite of its Mullen burst strenqth, its tensile strenath and its trapezoid tear strenath. More particularly, its Mullen burst strenqth is at least 650 psi (4482 kilopascals), its tensi]e strength is at least 300 lbs. (1334 newtons), and its trapezoid tear strength is at least 40 lbs. (178 newtons). Preferably its elongation at break is at ]east 25%. The high strenqth characteristic of the fabric is an essential characteristic of a fabric intended for use in an air baa where the air bag must be able to :.
withstand the initial shock of an explosive inflation and immediately thereafter the imPact of someone hittinq it as the passengers are thrown forward. It must withstand these forces without burstina, tearing or stretchinq to the point where - the air bag no lonqer serves its protective function~
~o be suitable for use in air bags, the fabric ~ must also be lightweight, thin and flexible as the :'- , .~
:: _ :
~ 4 air baq formed of the fabric must he capable of ~; being folded and compacted so as to fit within an extremely limited volume, such as that available within the steerina column or about the already crowded dashboard panel adiacent the driver. As a practical matter, the fabric must also be liqhtweiqht so that the air haq does not contribute unnecessarily to the weiaht of the car, ~hereby reducinq mileage. Thus the weiqht of the fabric is not more than 8.25 ounces per sauare yard (280 qm/m ), and the thickness is less than 0.016 inch (0.041 cm).
The properties of the fabric discussed herein are determined by Federal ~est Method Standard No.
191A and, in Particular, for permeability ~ethod 5450, for hurst strenqth Method 5122, for tensile strenath and elonaation, Method 5]00 Grah, for tear ,, .
strenqth Method 5136, for weiqht Method 504], and Eor thickness ~ethod 5030.
Accordinc to the present invention, ~he fabric is preferably formed of nylon or polyester yarn, with polYester yarn being preferred over nylon yarn for reasons unique to the present invention as will be explained hereinafter. Other thermoplastic yarn may be used for ~articular applications.
The cloth is woven of multifilament yarn not . :
~ qreater than 600 denier, and preferably 400-600 ~ ~ , i:: -. .
. :~.
~- 2014249 ,: 1 o denier, 100-300 filaments ~er yarn bundle. Lower denier yarns provide liqhtness and thinness, but ~` afford less strength and are more expensive as more yarn and more weavinq is reauired to provide the same coveraqe. Uigher denier yarn tends to produce : i a heavier and thicker fabric which is harder to fold and makes control of the oermeabilitY during the manufacturing process difficult, especially during the manufacturing process of the present invention as will be explained hereinafter. More particularly, the warp yarn is preferably 440/100/3 1/4 Z (that is, 440 denier, 100 filaments per yarn bundle, 3 1/4 turns per inch of yarn with a counter-clockwise twist), and the fill yarn is - lS preferably 440/100/0 (that is, 440 denier, 100 filaments per varn bundle, with a zero or "producer's" twist). A minimum of 100 filaments per yarn bundle is preferred.
In order to enhance the flexibility of the woven cloth, the cloth is woven in a basket weave, referably a 2 X 2 basket weave. It will be appreciated that the use of a basket weave, and in particular a 2 X 2 basket weave, increases the ~ermeability of the cloth. Nonetheless, the Drocessing of the cloth according to the present ~ :
invention so decreases its permeabilitY as to enable use of the 2 X 2 basket weave while still enablinq ~ .
: . . .
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-?'~- 201~2~9 .. --~,,, the cloth to meet the low ~ermeabilitY requirement.
As the forces exerted on the fabric may be in anv direction, it is preferred to use a weave which provides a balanced strength extenàing in all :
directions, such as a basket weave (as oPposed to an Oxford weave). Other weaves may be employed instead of a basket weave -- e.a., a 1 X 1 Plain weave. A 1 .~, X 1 plain weave is naturally tighter than a 2 X 2 basket weave and thus provides an even lower ~~ 10 permleability. Furthermore, the seam slippage is ^ decreased so that there is less windowing or opening of the seam during inflation, thereby improving the dynamic permeability of the fabric. While the 1 X 1 .~ .
Plain weave is naturally stiffer than a 2 X 2 basket weave, it has been found to be thinner by about 20%. The increased thinness compensates for the increased tiahtness so that the two weaves afford genera]ly comparable compactability.
The cloth is preferably woven, for a 2 X 2 hasket weave, about 52 ends/inch (20.5 ends/cm) and ~2 picks/inch (20.5 picks/cm) to provide a desirable tightness of the weave, althouqh qreater and fewer picks and ends per inch may be used. (About 51 ends/inch and 43 picks/inch are suitable for a 1 X 1 :: , .
~ ~ 25 rlain weave.) The optimum end and Pick count will ::~.,-depend to a large dearee upon the thickness (i.e., denier) of the yarn. For thick 600 denier yarn, the , , ~' -: .:
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end and pick count may be as much as 33~ less. For thin 40n denier yarn, a variation of + 5~ in end and pick count is acceptable. The tiqhter the weave (that is, the higher the end and pick count~ the less ~ermeable the cloth on the other hand, the looser the weave (that is, the lower the end and pick count), the less expensive the cloth in terms of both yarn material and weavinq costs).
- The desired low permeability of the fabric of the present invention is achieved by calenderinq the ~: .:
uncoated woven cloth on both sides thereof to reduce its permeability while at the same time retaininq its desirable characteristics of high strength, liqhtweiqht, thinness, and flexibility. While the .
calendering operation will be discussed hereinbelow in terms of reducinq the permeabilitY to not more than 1 CFM, clearly the parameters of the same calendering o~eration can be adiusted to provide a fabric having any permeability of not more than 3 C~M. It is believed that the calendering operation replasticizes the thermoplastic material of the :i woven cloth and sauashes and flattens the high ; points on both sides of the fabric to block the ,: .
- permeability-providing interstices. The calenderinq ~r~ 25 operation Produces a glossy sheen on the calendered -;h - I side of the fabric, so that a fabric which has been calendered on both sides is easily distinguishable ., ~ .
~ 2014249 i/
from uncalendered fabric or fahric which has been calendered on onlv one side.
Calenderina of the cloth on both sides thereof may be performed in a number of different ways de~endinq on such factors as the number of available existina calenders, the willinqness to create ~ specialized calenderina eauipment, the desirability - of continuous ~ersus batch ooeration, and the like.
As in a standard calenderinq operation, prior to . 10 calendering the cloth is typically scoured to clean \ the same (with detercent, anti-bacterial or anti~-fungal ingredients, dyes and other conventional materials added, as desired), and then dried and -~ heat set in a tenter oven (for example, at 250F). In order to exert pressure on the cloth as it passes through the calender, the cloth is insulated from the pressure roll (typicallY made of steel~ by a cushioninq roll (typical]y a steel roll havinq a number of coaxial disks of cotton paper thereabout). ~he hot roll (typically made of steel) on the other side of the cloth is heated to about : :~
350-370 F, for example, by hot oil flowinq ~ therethrough. In order to perform the second :.
calenderina operation -- that is, the calendering of the opposite side of the cloth -- in a hatch orocess, .he cloth may be inverted (to exchanqe sides) and passed through the same calendar a second '"
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: 2014249 time. Alternatively, in a continuous process, the cloth mav be oassed through an inverted second calender -- that is, a calender having the pressure and cushioning roll combination interchanged with the hot roll.
Referrina now to the drawinq, therein illustrated is a continuous process for the ::
calenderinc of cloth on both sides according to the ;::
present invention. The scoured and dried cloth 10 emeraing from a tenter oven (not shown) passes throuqh a conventional calender qenerally designated C including a pressure roll 12 bearing upwardly on a cush~oning roll 14 in turn bearing upwardly on the ;., ; bottom cloth surface, with a hot roll 16 bearinq downwardly on the upper cloth surface. Subseauently the cloth ]0, now calendered on the bottom surface, passes through an inverted calender generally designated C' includinq a pressure roll 12' bearing downwardly on a cushioning roll 14' in turn bearing downwardlv on the upper cloth surface, with a hot roll 16' bearing upwardly on the bottom cloth surface. The resultant cloth is calendered on both -:
- its top and bottom surfaces.
It will be appreciated that the two calenderina operations can he ~erformed usina a sinqle modified - calendar havina, for example, a cushionina roll and a hot pressure roll on each side of the cushionina ::;
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20142~9 ,:
roll. The cloth would pass initially hetween the cushionin~ roll and the ~irst hot ?ressure roll and then, after being ~wisted so that the calendered cloth surface which was adiacent the cushioninq roll ~` 5 is now remote from ~he cushioning roll, loop back between the cushioninq roll and the second hot pressure roll.
. .
Preferably the calenders exert a pressure of ~ .
65-75 psi (448-517 kilopascals) at a temperature of 350-370 F (177-188C1. A pressure of about 70 psi (483 kilopascals) and a temperature of about 360F (182) are preferred. Typically higher pressures are utilized in connection with lower temperatures, and lower pressures are utilized in conjunction with hiqher ~emDeratures. For exam~le, the calender maY exert a pressure of 65-80 tons per 70 inches of base (59.0-72.6 X 103 kiloqrams for a 178 cm base) at a nominal nip of 0.5 inch (1.27 cm), preferably about 70 tons (63.5 X 103 kilograms).
Where substantiallY hiqher calenderinq pressures are utilized, the low permeability is obtained onlv at the cost of the strength of the fabric which in effect becomes a plain sheet of plastic lackinq the strenqth of a woven. Where the :: .
calenderinq pressure is substantiallY lower, the calenderinq operation fails to squash and flatten : ' ~:
.
::::::
:::
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--- - ! 2 0 1 4 2 4 9 :
- the high spots of the cloth as necessary to achieve :::
low permeability.
:
,~s each calenderina o~eration subiects the cloth to an elevated temperature for only a short duration (e.q., approximately one second), the cloth is not thermally degraded as it is during a coatina operation, where the exposure of the cloth to an elevated temperature is prolonaed.
- - It is theorized that the calendering operation : :~ .
to a limited degree replasticizes the thermoplastic material of the woven cloth and mashes down the - hills or high spots of the woven cloth, thereby to :. .
close the adiacent interstices and so reduce the overa]l permeability of the cloth. Calendering on both sides of the cloth is essential as apparently ~~, ~ calenderinq on one side only does not effect :- .
blockage of each interstice (even when calendered twice on that side) while calendering on both sides) :-:, : :-~ substantially reduces and almost eliminates the :: : _ ~
~ 20 number of unblocked interstices. Alternativelv, it is possible that calendering on one side only, while - affecting substantially all interstices, fails to provide lO0~ blockinq of each interstice, and the calendering on the opposite side provides the additional blockaqe of each interstice necessary to substantially reduce the permeability of the cloth.
Indeed, the reason why it is preferred that the yarn '' , i:
-:
~-:
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of the present invention have a denier not exceeding 600, and oreferablY not exceedina 500, is that higher denier yarns have nigh spots which are ::::
difficult to mash down.
The reason why polyester cloth is preferred over nylon cloth in the present invention is that polyester retains its low permeability over an extended period of time (such as the 5 to 10 years of life which may be required for an automobile air baq). It will be appreciated that in a conventional air baq fabric where reduced permeability is :
obtained by coatinq, nylon remains a preferred material for a variety of reasons including ease of coating. On the other hand, in the fabric of the prPsent invention where an uncoated fabric achieves - . low permeability through calenderinq, the polyester .
fabric affords enhanced lonaevitv. It is theorized that the superiority of polYester over nvlon for the purpose of the present invention arises out of its :':
lower moisture reqain properties. Both nvlon and -polyester are hydrophobic fibers, and both are ~- thorouqhly dried in the tenter oven prior to - ~ calenderina. Over a period of time after ~::: ,,.
~ calendering (during the S-l0 year anticioated :
-- 25 lifetime of the air baa), the nylon fabric will ~ exhibit a nigher moisture regain (about ~.5%) .:
~- relative to the polyester (about 0.4~). As the :~
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201424~
nylon fabric regains moisture, it also tends to resume its oriqinal woven configuration, with the one-time hills crushed bv the calendering o~eration into or over the interstices departing the interstices and resuming their prior orientation, thus allowinq a return to a higher permeability.
Further, while the nYlon fabric may initiallv exhibit a higher tensile strength (175-183 lbs.) than the polyester fabric (148 lbs.), after oven aging at 300F for ~8 hours the nylon fabric tensile strenqth degrades sharply (to 83-87 lbs.) while the polyester fabric tensile strenqth remains substantially constant (at 148 lbs.).
~ This followinq example illustrates the relative - 15 effects of calendering both sides of a fabric, - relative to calenderinq only one side of the fabric.
A test cloth had a warp of 440/100/3 1/4 Z yarn and a fill of 440/100/0 yarn. The cloth was a 2 X 2 basket weave.
Calendering was performed at a pressure of 70 ~-~ psi and 360 F for ~each run. One sample of the fabric was calendered twice on one side, and other sample of the fabric was calendered once on each side. Permeability of the fabric was measured u~ before any calenderina operation, after the Eirst calenderinq operation, and after the second '.~ :-: -, ~: :
::
:
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calenderinq operation. The resultamt permeabilities of the fabric samples are indicated in the Table.
TABLE
CalenderingCalenderinq Same Opposite Side, CFMSides, CFM
Before Calenderinq 24.20 22.90 After 1st Calendering 1.82 1.63 After 2nd Calendering 1.42 q.62 Thus, calendering on one side produced a verv :::
substantial lesseninq of permeability. While a second calenderinq on that one side afforded a ~ further small decrement in permeabilit~, a second .-~
calendering on the other side of the fabric produced a substantial decrease in permeability, one '; . 15 sufficient to reduce the permeability below the l .::::-CFM level. In other words, when calenderinq is -- performed on opposite sides of the fabric, ~he second calendering is more effective than when calendering is performed twice on the same side of the fabric. This is true both in terms of the absolute and relative decreases in permeability resulting from the second calenderinq operation. In absolute terms, the second calenderina operation (on the opposite side) produced a decrease in ~`- 25 permeability which was 2 l/2 times that Prod~ce~
when calenderinc was performed twice on the same ~ side; in relative terms (as a percentage of the :
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201~2~9 ` 20 !
~~, permeability remaining after the first calenderina :-, ~- operation), the decrease in permeability was almost . .,~ .
~ three times greater.
`~ After calenderinq on opposite sides, the cloth had 54 ends per inch and 51 picks per inch, and had ~. , .. ,__, ,- a Mullen burst strength of 905 psi, a tensile strength of 548-558 lbs., a trapezoid tear strength of 208-372 lbs., an elonqation at break of 38-50%, a weiqht of 7.22 oz./sauare yard and a thickness of 0.010 inch.
By way of comparison, a 1 X 1 plain polYester weave cloth of similar yarns had, after similar calendering on both sides, 51 ends per inch and 43 ::
picks per inch and had a permeability of 0.21 CFM.
: ~ .
` 15 The cloth had a Mullen burst strength of 825 psi, a :~ :
tensile strenqth of 494-552 lbs., a trapezoid tear , strength of 64-108 lbs., an elonqation at break of 36-37%, a weight of 6.29 oz./sauare yard and a :~ , thickness of 0.0078 inch.
:,:.
~ 20 To summarize, the present invention provides an - uncoated woven fabric which is stronq, lightweiqht, :: ~
thin and flexible, yet has an extremelY low permeability -- namely, a permeability not higher than 1 CFM -- so as to render it suitable for use in 25 air baas even accordinq to pro~osed new standards.
Now that the preferred embodiments of the :
present invention have been shown and described in ,, : ~
:
i ~3 detail, various modifications and improvements thereon will become readily a~parent to those - skilled in the art. Accordin~ly, the appended claims are to be construed broadly in a manner : S consistent with the spirit and scope of the invention herein.
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Claims (23)
1. A strong, lightweight, thin, flexible fabric of low permeability comprising an uncoated woven cloth characterized by a permeability of not more than one cubic foot of air per minute per square foot of cloth (0.5 cm3/sec/cm2) at a pressure drop of 0.5 inch of water (1.27 cm) across the cloth.
2. The fabric of Claim 1 further characterized by a Mullen burst strength of at least 650 psi (4482 kilopascals), a tensile strength of at least 300 lbs. (1334 newtons), a trapezoid tear of at least 40 lbs. (178 newtons), an elongation at break of at least 25%, a weight of not more than 8.25 oz/square yard (280 gm/m2), and a thickness of less than 0.016 inch (0.041 cm).
3. The fabric of claim 1 wherein said cloth is woven in a 1 X 1 plain weave.
4. The fabric of Claim 3 wherein said cloth is woven in a 2 X 2 basket weave.
5. The fabric of Claim 1 wherein said cloth is woven about 51-52 ends/inch by about 43-52 picks/inch (20 ends/cm by 17-20 picks/cm).
6. The fabric of Claim 1 wherein said cloth is polyester.
7. The fabric of Claim 1 wherein said cloth is woven of not greater than 600 denier multifilament yarn.
8. The fabric of Claim 7 wherein said cloth is woven of 400-600 denier multifilament yarn.
9. The fabric of Claim 8 wherein said cloth is woven from yarn having 100-300 filaments.
10. The fabric of Claim 9 wherein said cloth is woven from polyester filament yarn.
11. The fabric of Claim 1 wherein said cloth is calendered on both sides.
12. A strong, lightweight, thin, flexible fabric of low permeability comprising an uncoated, woven, high strength, lightweight, thin, flexible cloth calendered on both sides to reduce the permeability to not more than one cubic foot of air per minute per square foot of cloth (0.5 cm3/sec/cm) at a pressure drop of 0.5 inch of water (1.27 cm) across the cloth.
13. A strong, lightweight, thin, flexible fabric of low permeability comprising an uncoated woven cloth of polyester calendered on both sides to reduce the permeability to not more than one cubic foot of air per minute per square foot of cloth (0.5 cm3/sec/cm) at a pressure drop of 0.5 inch of water (1.27 cm) across the cloth, and characterized by a Mullen burst strength of at least 650 psi (4482 kilopascals), a tensile strength of at least 300 lbs. (1334 newtons), a trapezoid tear of at least 40 lbs. (178 newtons), an elongation at break of at least 25%, a weight of not more than 8.25 oz/square yard (280 gm/m), and a thickness of less than 0.016 inch (0.041 cm), woven of 400-600 denier multifilament yarn, having 100-300 filaments per yarn bundle.
14. A method of making a strong, lightweight, thin, flexible fabric of low permeability comprising the steps of:
(A) providing an uncoated, woven, strong, lightweight, thin, flexible cloth of high permeability and (B) calendering the cloth on both sides to reduce the permeability to not more than three cubic feet of air per minute per square foot of cloth (1.5 cm3/sec/cm) at a pressure drop of 0.5 inch of water (1.27 cm) across the cloth.
(A) providing an uncoated, woven, strong, lightweight, thin, flexible cloth of high permeability and (B) calendering the cloth on both sides to reduce the permeability to not more than three cubic feet of air per minute per square foot of cloth (1.5 cm3/sec/cm) at a pressure drop of 0.5 inch of water (1.27 cm) across the cloth.
15. The method of Claim 14 wherein the cloth is calendered to reduce its permeability while providing a Mullen burst strength of at least 650 psi (4482 kilopascals), a tensile strength of at least 300 lbs. (1334 newtons), a trapezoid tear of at least 40 lbs. (178 newtons), an elongation at break of at least 25%, a weight of not more than 8.25 oz/sauare yard (280/gm/m) and a thickness of less than 0.016 inch (0.041 cm).
16. The method of Claim 14 wherein the cloth is calendered on both sides to reduce the permeability to not more than one cubic foot of air per minute per square foot of cloth (0.5 cm3/sec/cm) at a pressure drop of 0.5 inch of water (1.27 cm) across the cloth.
17. The method of Claim 14 wherein the cloth is calendered in a calender exerting a pressure of 65-75 psi (448-517 kilopascals) at a temperature of about 350-370°F (177-188°C).
18. The method of Claim 17 wherein the cloth is calendered in a calender exerting a pressure of 70 psi (483 kilopascals) at a temperature of about 360°F (182°C).
19. The method of Claim 14 wherein the cloth is calendered in a calender exerting 65-80 tons/70 inch base (59.0-72.6 X 103 kilograms/178 cm) at a nominal nip of 0.5 inch (1.27 cm) at a temperature of 350°-370°F (177-188°C).
20. The method of Claim 19 wherein the cloth is calendered in a calender exerting about 70 tons (63.5 X 103 kilograms) at a temperature of about 360°F (182°C).
21. A strong, lightweight, thin, flexible fabric of low permeability when prepared from an un-coated, woven, strong, lightweight, thin, flexible cloth of high permeability according to the calendering method of Claim 14.
22. A method of making a strong, lightweight, thin, flexible fabric of low permeability comprising the steps of:
(A) providing an uncoated, woven, strong, lightweight, thin, flexible cloth of high permeability;
and (B) calendering the cloth on both sides in a calendar exerting a pressure of 65-75 psi (448-517 kilo-pascals) at a temperature of 350-370°F (177-188°C) to reduce the permeability to not more than three cubic feet of air per minute per square foot of cloth (1.5 cm3/sec/cm) at a pressure drop of 0.5 inch of water (1.27 cm) across the cloth while retaining a Mullen burst strength of at least 650 psi (4482 kilopascals), a tensile strength of at least 300 lbs. (1334 newtons), a trapezoid tear of at least 40 lbs. (178 newtons), an elongation at break of at least 25%, a weight of not more than 8.25 oz/square yard (280 gm/m) and a thick-ness of less than 0.016 inch (0.041 cm).
(A) providing an uncoated, woven, strong, lightweight, thin, flexible cloth of high permeability;
and (B) calendering the cloth on both sides in a calendar exerting a pressure of 65-75 psi (448-517 kilo-pascals) at a temperature of 350-370°F (177-188°C) to reduce the permeability to not more than three cubic feet of air per minute per square foot of cloth (1.5 cm3/sec/cm) at a pressure drop of 0.5 inch of water (1.27 cm) across the cloth while retaining a Mullen burst strength of at least 650 psi (4482 kilopascals), a tensile strength of at least 300 lbs. (1334 newtons), a trapezoid tear of at least 40 lbs. (178 newtons), an elongation at break of at least 25%, a weight of not more than 8.25 oz/square yard (280 gm/m) and a thick-ness of less than 0.016 inch (0.041 cm).
23. A strong, lightweight, thin, flexible fabric of low permeability when prepared from an un-coated, woven, strong, lightweight, thin, flexible cloth of high permeability according to the calendering method of Claim 22.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002014249A CA2014249C (en) | 1990-04-10 | 1990-04-10 | Low permeability fabric and method for making same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002014249A CA2014249C (en) | 1990-04-10 | 1990-04-10 | Low permeability fabric and method for making same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2014249A1 CA2014249A1 (en) | 1991-10-10 |
| CA2014249C true CA2014249C (en) | 1997-05-13 |
Family
ID=4144727
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002014249A Expired - Lifetime CA2014249C (en) | 1990-04-10 | 1990-04-10 | Low permeability fabric and method for making same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2014249C (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017079499A1 (en) | 2015-11-06 | 2017-05-11 | Invista North America S.Ar.L. | Low permeability and high strength fabric and methods of making the same |
| WO2018204154A1 (en) | 2017-05-02 | 2018-11-08 | Invista Textiles (U.K.) Limited | Low permeability and high strength woven fabric and methods of making the same |
| US11708045B2 (en) | 2017-09-29 | 2023-07-25 | Inv Performance Materials, Llc | Airbags and methods for production of airbags |
-
1990
- 1990-04-10 CA CA002014249A patent/CA2014249C/en not_active Expired - Lifetime
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017079499A1 (en) | 2015-11-06 | 2017-05-11 | Invista North America S.Ar.L. | Low permeability and high strength fabric and methods of making the same |
| US11214895B2 (en) | 2015-11-06 | 2022-01-04 | Inv Performance Materials, Llc | Low permeability and high strength fabric and methods of making the same |
| WO2018204154A1 (en) | 2017-05-02 | 2018-11-08 | Invista Textiles (U.K.) Limited | Low permeability and high strength woven fabric and methods of making the same |
| EP3831671A1 (en) | 2017-05-02 | 2021-06-09 | INVISTA Textiles (U.K.) Limited | Low permeability and high strength woven fabric |
| US11634841B2 (en) | 2017-05-02 | 2023-04-25 | Inv Performance Materials, Llc | Low permeability and high strength woven fabric and methods of making the same |
| US11708045B2 (en) | 2017-09-29 | 2023-07-25 | Inv Performance Materials, Llc | Airbags and methods for production of airbags |
Also Published As
| Publication number | Publication date |
|---|---|
| CA2014249A1 (en) | 1991-10-10 |
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Effective date: 20100410 |