Note: Descriptions are shown in the official language in which they were submitted.
CA 02801482 2012-12-03
:11:1DESCRIPTION
E. i Invention Title':.1
FABRIC FOR AIRBAG, USING POLYETHYLENE TEREPHTHALATE FIBER
WITH EXCELLENT HEAT RESISTANCE
1Technical Fieldr I
The present invention relates to a fabric for an airbag using a polyethylene
terephthalate fiber, and particularly, to a fabric for an airbag having
enhanced thermal
resistance and instantaneous thermal strain rate, which is manufactured using
a
polyethylene terephthalate fiber for an airbag manufactured by controlling the
strength and elongation of the polyethylene terephthalate fiber to replace a
conventional fabric for an airbag using a yarn formed of nylon 66.
FilBackground Artl
An airbag requires characteristics of low air permeability to easily rupture
in a
car crash, and energy absorbability to prevent damage to and bursting of the
airbag
itself. In addition, to be more easily stored, characteristics relating to
foldability of
a fabric itself are required. As a suitable fiber having the above-
described
characteristics, nylon 66 has generally been used. However, recently, in order
to
save on cost, attention on fibers other than nylon 66 has been increasing.
As a fiber capable of being used for an airbag, polyethylene terephthalate may
be used. However, when polyethylene terephthalate is used as a yarn for an
airbag,
seams rupture during airbag cushion module tests. To solve this problem, it is
important to use a polyethylene terephthalate yarn that does not degrade the
energy
absorbability of an airbag. In addition, it is necessary to improve
flexibility of the
fabric for an airbag using a polyethylene terephthalate fiber to be easily
stored.
rl D i sc los u
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CA 02801482 2012-12-03
ii Technical Prob lem
The present invention is directed to providing a fabric for an airbag using
polyethylene terephthalate, which has excellent energy absorbability resulting
in
fewer ruptures of outer seams during an airbag cushion development tests, and
is
more easily stored.
LiTechnical Solution Li
According to an exemplary embodiment of the present invention, a fabric for
an airbag including a polyethylene terephthalate fiber manufactured by
spinning a
polyethylene terephthalate chip having an intrinsic viscosity of 0.8 to 1.3
dlig is
provided, The fabric for an airbag has a thermal resistance of 0.45 to 0.65
seconds
at 350 C, which is calculated by the following Equation.
[Equation 1]
Thermal Resistance (sec) of Fabric = THr2
In Equation 1, T1 is the time in which a steel rod heated to 350 C falls from
10
cm above the fabric through the fabric, and 12 is the time in which the same
steel rod
falls from the same height.
According to another exemplary embodiment of the present invention, a fabric
for an airbag including a polyethylene terephthalate fiber manufactured by
spinning a =
polyethylene terephthalate chip having an intrinsic viscosity of 0.8 to 1.3
cll/g is
provided. The fabric for an airbag has a thermal resistance of 0.75 to 1.0
seconds at
450 C, which is calculated by the following Equation, and an instantaneous
thermal
strain rate of 1.0 to 5.0%.
[Equation 21
Thermal Resistance (sec) of Fabric = T3-14
2
=
=
CA 02801482 2012-12-03
In Equation 2, T3 is the time that a steel rod heated to 450 C falls from 10
cm
above the fabric through the fabric, and T4 is the time that the same steel
rod falls
from the same height.
According to still another exemplary embodiment of the present invention, the
fabric for an airbag has a stiffness of 5.0 to 15.0 N.
According to yet another exemplary embodiment of the present invention, the
polyethylene terephthalate fiber has a strength of 8.0 to 11.0 g/d, and an
elongation
of 15 to 30% at room temperature.
According to yet another exemplary embodiment of the present invention, the
polyethylene terephthalate fiber has an instantaneous thermal strain rate of
1.0 to
5.0%, and a filament size of 4.5 deniers or less.
7IAdvantageous Effectscil
The present invention provides a polyethylene terephthalate fabric for an
airbag,
which overcomes the lack of flexibility, which is a disadvantage of a
conventional
fabric for an airbag, and has better thermal resistance. As a result, an
airbag module
manufactured using the fabric for an airbag can be more easily stored and
rarely
bursts due to pressure and heat instantaneously applied by a high temperature
expanding gas during airbag development tests.
=
ri Best Modell
The present invention provides a polyethylene terephthalate fabric for an
airbag
manufactured by manufacturing a polyethylene terephthalate fiber for an airbag
by
controlling the strength and elongation of the polyethylene terephthalate
fiber,
thereby obtaining excellent thermal resistance and instantaneous thermal
strain rate.
Accordingly, outer seams rupture less frequently during airbag cushion
development
tests, and the foldability and storability of the fabric for an airbag are
improved.
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In the present invention, the fabric for an airbag uses a polyethylene
terephthalate multifilament obtained by spinning a polyethylene terephthalate
chip
having an intrinsic viscosity (IV) of 0.8 to 1.3 dl/g to safely absorb
instantaneous
impact energy of an exhausted gas generated due to explosion of gunpowder in
the
airbag. A polyester yarn having an intrinsic viscosity (IV) of less than 0.8
dl/g is
not suitable because the polyester yarn does not have sufficient toughness to
be used
as an airbag.
A resin for producing a synthetic fiber multifilament for an airbag may be
selected from the group consisting of polymers such as polyethylene
terephthalate,
polybutylene terephthalate, polyethylene naphthalate, polybutylene naphtha
late,
polyethylene-1,2-bis(phenoxy)ethane-4,4-dicarboxylate, and poly(1,4-
cyclohexylene-dimethylene terephthalate); copolymers including at least one of
the
polymers as a repeated unit, such as polyethylene terephthalate/isophthalate
copolyester, polybutylene terephthalate/naphthalate copolyester, and
polybutylene
terephthalate/decane diearboxylate copolyester; and a mixture of at least two
of the
polymers and copolymers. Among these, in the present invention, a polyethylene
terephthalate resin is most preferably used in terms of mechanical properties
and the
formation of a fiber.
The polyethylene terephthalate fiber for an airbag of the present invention
may
have a strength of 8.0 to 11.0 g/d and an elongation of 15 to 30% at room
temperature. When a strength of the polyethylene terephthalate fiber for an
airbag
of the present invention is less than 8.0 g/d, the polyethylene terephthalate
fiber is
not suitable for the present invention because of low tensile and tearing
strengths of
the manufactured fabric for an airbag. =
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CA 02801482 2012-12-03
In addition, when the elongation of the fiber is less than 15%, energy
absorbability is decreased when an airbag cushion is suddenly expanded, and
thus the
airbag cushion bursts, which is not suitable. When a yarn is manufactured to
have
the elongation of' the fiber of more than 30%, sufficient expression of the
strength is
difficult due to the characteristics of a process olmanufacturing a yarn.
The polyethylene terephthalate fiber for an airbag of the present invention
may
have a filament size of 4.5 deniers or less, and preferably 3 deniers or less.
Generally, as a fiber having a smaller filament size is used, the obtained
fabric
becomes flexible, thereby achieving excellent foldability and better
storability. In
addition, when the filament size is smaller, covering properties are enhanced
at the
same time. As a result, air permeability of the fabric may be inhibited. When
the
filament size is more than 4.5 deniers, the fabric has degraded foldability
and
storability, and low air permeability, and thus the fabric cannot properly
serve as a
fabric for an airbag.
The polyethylene terephthalate fiber for an airbag of the present invention
may
have an instantaneous thermal strain rate of 0.1 to 5.0%, and preferably 2.0
to 4.0%
at 100 C. When the instantaneous thermal strain rate of the fiber is less
than 1.0%,
the absorbability of energy applied when the airbag cushion is expanded due to
a
high temperature gas is degraded, and thus the airbag cushion bursts easily.
In
addition, when the instantaneous thermal strain rate of the fiber is more than
5.0%, a
length of the fiber is increased at high temperature, and thus seams of the
airbag
cushion rupture when it is expanded due to a high temperature gas. Therefore,
an
uncontrolled expanding gas is leaked.
In the uncoated polyethylene terephthalate fabric whose density is 50 wefts or
warps per inch after a scouring and contracting process, stiffness may be
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CA 02801482 2012-12-03
approximately 5.0 to 15.0 N, and preferably 6.0 to 9.0 N when evaluated by
circular
bend measurement. When the stiffness is more than 15.0 N, the fabric becomes
stiff,
and thus is difficult to store in the manufacture of the airbag module and
degraded in
developing performance of the airbag cushion.
In the uncoated polyethylene terephthalate fabric whose density is 50 wefts or
warps per inch after a scouring and contracting process, thermal resistance
measured
using a rod heated at 350 C in a hot rod test may be 0.75 to 1.0 seconds.
When the
thermal resistance measured at 350 C is less than 0.75 seconds, the thermal
resistance of the fabric for an airbag is too low to withstand a high
temperature gas in
the development of the airbag cushion, and thus outer seams of the airbag
easily
rupture. When the thermal resistance measured at 350 C is more than 1.0
second,
since a polyethylene terephthalatc yarn having a larger filament size is
necessarily
used, the stiffness of the fabric is increased, and thus the fabric for an
airbag is
difficult to store in the module.
In the uncoated polyethylene terephthalate fabric whose density is 50 wefts or
warps per inch after a scouring and contracting process, thermal resistance
measured
using a steel rod heated to 450 C in a hot rod test may be 0.45 to 0.65
seconds.
When the thermal resistance measured at 450 C is less than 0.45 seconds, the
thermal resistance of the fabric for an airbag is too low to withstand a high
temperature gas in the development of the airbag cushion, and thus outer seams
of
the airbag easily rupture. When the thermal resistance measured at 450 C is
more
than 0.65 seconds, since a polyethylene terephthalate yarn having a larger
filament
size is necessarily used, the stiffness of the fabric is increased, and thus
the fabric for
an airbag is difficult to store in the module.
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CA 02801482 2012-12-03
In the present invention, the fabric may be woven with the polyethylene
terephthalate fiber as a plain fabric having a symmetrical structure.
Alternately, to
obtain more favorable physical properties, the fabric may be woven as a 2/2
panama
fabric having a symmetrical structure using a yarn having a smaller linear
density.
The woven fabric may be coated with a coating agent selected of silicon-,
polyurethane-, acryl-, neoprene-, and chloroprene-based coating agents at a
weight of
to 60 g/m2 to secure low air permeability, which is suitable for the fabric
for an
airbag.
Evaluation of physical properties in Examples and Comparative Examples were
10 performed as follows:
1) Intrinsic Viscosity (IV.)
0.1 g of a sample was dissolved in a reagent prepared by mixing phenol and
1,1,2,2-tetrachloroethanol in a weight ratio of 6:4 (90 C) for 90 minutes.
The
resulting solution was transferred to an Ubbelohde viscometer and maintained
in a
15 constant temperature oven at 30 C for 10 minutes, and a drop time of the
solution
was measured using a viscometer and an aspirator. A drop time of a solvent was
also measured as described above, and then R.V. and 1.V. values were
calculated by
the following equations.
R.V. = Drop Time of Sample/Drop Time of Solvent
1.V. = 1/4x[(R.V.-1)/C1+3/4x(In R.V./C)
In the above equation, C is the concentration (g/100 ml) of the sample in the
solution.
2) Measurement of Instantaneous Thermal Strain Rate
A bundle of filaments having a thickness of approximately 59 deniers was
made by randomly selecting filaments from a multi filament yarn. The bundle of
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CA 02801482 2014-04-30
. ,
filaments was mounted on a TA instrument (model name: TMS Q4OO)TM to
have a length of 10 mm, and then a stress of 1.0 gf/den was applied thereto. 2
minutes after the application of a stress, a test started and a temperature
was rapidly
increased from 30 to 100 C for 30 minutes. An instantaneous thermal strain
rate
was obtained by dividing a length increment of the sample when the temperature
approached 100 C by an initial length of the sample, and is shown as a
percentage.
3) Measurement of Stiffness of Fabric
The stiffness of a fabric was measured by circular bend measurement
according to the specification of ASTM D4032. Here, the stiffness was measured
with respect to weft and warp directions, and an average of the values
obtained in the
weft and warp directions is shown in units of Newtons (N).
4) Method of Measuring Thermal Resistance of Fabric (350 C Hot rod test)
A cylindrical steel rod having a weight of 50 g and a diameter of 10 mm was
heated to 350 C and then dropped vertically from 10 cm above a fabric for an
airbag.
Here, the time in which the heated rod fell through the fabric was T1, and the
time in
which the rod fell without the fabric was 12. The thermal resistance was
measured
by the following equation. Here, one layer of the unfolded fabric for an
airbag was
used.
[Equation 1]
Thermal Resistance (Sec.) of Fabric = T1¨T2
5) Method of Measuring Thermal Resistance of Fabric (450 C Hot rod test)
A cylindrical steel rod having a weight of 50 g and a diameter of 10 mm was
heated to 450 C and then dropped vertically from 10 cm above a fabric for an
airbag.
Here, the time in which the heated rod fell through the fabric was 13, and the
time in
which the rod fell without the fabric was T4. The thermal resistance was
measured
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CA 02801482 2012-12-03
by the following equation. Here, one layer of the unfolded fabric for an
airbag was
used.
[Equation 2]
Thermal Resistance (Sec.) of Fabric = Ty-T4
6) Method of Measuring Strength and Elongation of Yarn
A yarn sample was left in a constant temperature and constant humidity
chamber under standard conditions, that is, a temperature of 25 C and a
relative
humidity of 65% for 24 hours, and tested by a method of ASTM 2256 using a
tension
tester.
7) Weaving and Coating of Fabric
A plain fabric was woven with a filament yarn to have a yarn density of 50
wefts or warps per inch in both of well and warp directions. A raw fabric was
scoured and contracted in aqueous baths which were gradually set from 50 to 95
C
using a continuous scouring machine, and then treated at 200 C for 2 minutes
by
thennomechanical treatment. Afterward, the fabric was coated with a silicon-
based
coating agent at a weight of 25 g/m2.
8) Airbag Cushion Development Test
A driver airbag (DAB) module was manufactured with a coated fabric for an
airbag, and subjected to a static test within several minutes after being left
at 85 C
for 4 hours. Here, a pressure of a powder inflator was 180 kPa, and when the
tearing of the fabric, forming of a pin hole and burning of the fabric were
not shown
after the development test, it was evaluated as "Pass." However, when any one
of
the tearing of the fabric, forming of a pin hole in a seam and burning of the
fabric
was shown, it was evaluated as "Fail."
n Mode for Inventionri
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Hereinafter, the present invention will be described in detail with respect to
Examples, but the scope of the present invention is not limited to the
following
Examples and Comparative Examples.
Example 1
A raw fabric for an airbag was manufactured with a polyethylene terephthalate
yarn having the characteristics listed in Table 1 by plain-weaving using a
rapier loom
to have a fabric density of 50 wefts or warps per inch in both of weft and
warp
directions.
Example 2
A raw fabric for an airbag was manufactured with a polyethylene terephthalate
yarn having the characteristics listed in Table I by the method as described
in
Example 1.
Example 3
A raw fabric for an airbag was manufactured with a polyethylene terephthalate
yarn having the characteristics listed in Table I by the method as described
in
Example 1.
Comparative Example 1
A raw fabric for an airbag was manufactured with a nylon 66 yarn having the
characteristics listed in Table I by plain-weaving using a rapier loom to have
a fabric
density of 50 wefts or warps per inch in both of weft and warp directions.
Comparative Example 2
A raw fabric for an airbag was manufactured with a polyethylene terephthalate
yarn having the characteristics listed in Table 1 by the method as described
in
Comparative Example I.
Comparative Example 3
=
CA 02801482 2012-12-03
A raw fabric for an airbag was manufactured with a polyethylene terephthalate
yarn having the characteristics fisted in Table 1 by the method as described
in
Comparative Example 1.
Example 4
The raw fabric manufactured in Example I was scoured and contracted in
aqueous baths gradually set from 50 to 95 C using a continuous scouring
machine,
and then treated at 200 C for 2 minutes by thermomechanical treatment. In an
uncoated state, the fabric was measured in stiffness, thermal resistance at
350 C and
thermal resistance at 450 C, the results of which arc shown in Table 2.
In addition, the manufactured fabric was coated with a silicon-based coating
agent at a weight of 25g/m2, and thermally treated at 180 C for 2 minutes. An
airbag cushion was made with the thermally-treated fabric, and subjected to a
development test for the airbag cushion. The test results and storability in a
module
are shown in Table 2.
Example 5
The raw fabric manufactured in Example 2 was treated by the method
described in Example 4. Physical properties, results of an airbag cushion
development test and storability in a module of the manufactured fabric are
shown in
Table 2.
Example 6
The raw fabric manufactured in Example 3 was treated by the method
described in Example 4. Physical properties, results of an airbag cushion
development test and storability in a module of the manufactured fabric are
shown in
Table 2.
Comparative Example 4
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The raw fabric manufactured in Comparative Example I was scoured and
contracted in aqueous baths gradually set from 50 to 95 C using a continuous
scouring machine, and then treated at 200 C for 2 minutes by thermomechanical
treatment. In an uncoated state, the fabric was measured in stiffness, thermal
resistance at 350 C and thermal resistance at 450 C, the results of which
are shown
in Table 2.
In addition, the manufactured fabric was coated with a silicon-based coating
agent at a weight of 25g/m2, and thermally treated at 180 C for 2 minutes. An
airbag cushion was made with the thermally-treated fabric, and subjected to a
development test for the airbag cushion. The test results and storability in a
module
are shown in Table 2.
Comparative Example 5
The raw fabric manufactured in Comparative Example 2 was treated by the
method described in Comparative Example 3. Physical properties, results of an
airbag cushion development test and storability in a module of the
manufactured
fabric are shown in Table 2.
Comparative Example 6
The raw fabric manufactured in Comparative Example 3 was treated by the
method described in Comparative Example 3. Physical properties, results of an
airbag cushion development test and storability in a module of the
manufactured
fabric are shown in Table 2.
[Table I]
Kind Intrinsic
Instantaneous
Filament Strength Elongation
Material of Viscosity Thermal
Strain
size (den) (g/den) (%)
Yarn (dl/g) Rate (%)
12
CA 0 2 8 01 4 8 2 2 01 2-1 2-0 3
500 -
Polyethylene
Example 1 6/182 1.06 2.7 8,4 25.0 2.8
terephthalate
500
Polyethylene
Example 2 6/182 I .06 2.7 11.0 18.0 3.5
terephthalate
500
Polyethylene
Example 3 6/120 1.06 4.2 9.0 22.6 2.3
terephthalate =
Comparative 420 -
Nylon 66 6.2 9.7 22.0 1.8
Example 1 6/68
Comparative Polyethylene 420
1.06 6.2 7.8 14.0 0.4
Example 2 terephthalate 6/68
Comparative Polyethylene 500
1.06 5.2 7.5 12.0 0.6
Example 3 terephthal ate 6/96
[Table 21
Thermal Thermal - Airbag Cushion Ability to be
Stillness of
Resistance at Resistance at Development stored in
Fabric
Fabric (N)
350 C (sec.) 450 C (sec.) Test for Airbag
Example 4 7.4 0.94 0.56 Pass Good
Example 5 7.6 0.97 0.62 Pass Good
Example 6 13.7 0.87 0.50 Pass Moderate
Comparative -
6.9 0.79 0.46 Pass Good
Example 4
Comparative
15.4 0.69 0.39 Fail Bad
Example 5
Comparative
17.5 0.73 0.42 Fail Bad
Example 6
13
