Textiles: weaving – Fabrics – Special shape
Reexamination Certificate
2002-01-11
2004-12-21
Singh, Arti R. (Department: 1771)
Textiles: weaving
Fabrics
Special shape
C428S034100, C428S034300, C428S034500, C428S034600, C428S034700, C428S035700, C428S036100, C428S036200, C428S102000, C428S103000, C428S104000, C428S105000, C428S107000, C280S728100, C280S728300, C280S729000, C280S730100, C280S730200, C139S42000D, C139S408000, C139S409000, C139S410000, C139S411000, C139S412000, C139S413000, C139S414000, C139S415000, C139S416000, C139S417000, C139S418000, C139S419000, C139S421000, C139S422000, C139S423000
Reexamination Certificate
active
06832633
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high density fabric for air bag and method for manufacturing high density fabric which is suitable for a fabric of air bag, one of safety apparatuses of automobile, and more specifically to a high density fabric for air bag having low air permeability, as well as excellent air permeability characteristics under high pressures while maintaining necessary mechanical properties.
2. Description of the Related Art
In recent years, the number of automobiles equipped with an air bag as a car safety component has rapidly increased in association with rising awareness of safety of passengers. An air bag is useful for protecting a passenger at the time of collision accident of automobile by sensing the collision with a sensor and causing an inflator to generate gas of high temperature and pressure to allow the air bag to rapidly expand.
Conventionally, base fabrics on which synthetic rubber such as chloroprene, chlorosulfonated olefin, silicone have been used for the purpose of achieving heat resistance, air insulation (permeability) and flame resistance.
However, such coated base fabrics had many drawbacks when used as a base fabric for air bag. That is, the weight of base fabric increases, the softness is deteriorated, the production cost increases and recycling is difficult. Though some of silicone-coated base fabrics currently used have considerably improved the above-mentioned drawbacks, they are not still satisfactory.
For this reason, non-coated base fabrics for air bag on which coating is not made are latest mainstream, and various proposals have been made for achieving reduced weight, desirable storability and lower air permeability. Under such current circumstances, base fabrics of further reduced weight and lower air permeability are requested as non-coated air bag base fabric.
Furthermore, in case of weaving high density fabric, when the weaving speed is increased in an attempt to increase productivity, yarn damages are increased due to frictions between the fibers and with reed, with the result that problems occur such as to give undesirable effects to the physical properties of the foundation. There is strong desire to obtain measures for settling these points.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a high density fabric suitable for air bag and method for manufacturing high density fabric, by obtaining a fabric of low air permeability and reduced weight having a stable fabric strength mechanical property and excellent air permeability characteristics under high pressures that has not been solved by the above-mentioned conventional methods.
Means for solving the above object, that is, the first aspect of the present invention is a high density fabric for air bag wherein air permeability under a differential pressure of 50 kPa is 2.5 L/cm
2
/min. or less, and air permeability index (50 kPa) calculated by the formula (1) is 1.2 or more.
Air permeability index (50 kPa)=(Log (
Q
(55 kPa))−Log(
Q
(45 kPa)))/(Log55−Log45) (1)
Q
(55 kPa):air permeability under 55 kPa differential pressure (1/cm
2
/min.)
Q
(45 kpa):air permeability under 45 kPa differential pressure (1/cm
2
/min.)
The second aspect of the invention is the high density fabric for air bag according to the first aspect, wherein the air permeability (50 kPa) is 1.3 or more, the third aspect of the invention is the high density fabric for air bag according to the first aspect, wherein the difference in crimp percentage between warp and weft is 4% or more, the fourth aspect of the invention is the high density fabric for air bag according to the first aspect, wherein the degree of intermingle of raw yarn before weaving is 10 to 30 times/m, and the fifth aspect of the invention is the high density fabric for air bag according to the first aspect, where in a cover factor calculated by the formula (2) in the high density fabric is in the range of 1800 to 2400.
Cover factor=
A
0.5
×(
W
1
)+
B
0.5
×(
W
2
) . . . (Formula 2)
A: Coarseness of warp (dtex)
B: Coarseness of weft (dtex)
W
1
: Density of warp (stripes/in.)
W
2
: Density of weft (stripes/in.)
The sixth aspect of the invention is the high density fabric for air bag according to the first aspect, wherein the degree of intermingle of warp or weft of the high density fabric is 8 times/m or less.
Now, characterizations of the high density fabric suitable for air bag according to the present invention will be explained in detail. The difference in crimp percentage between warp and weft constituting the fabric is preferably 4% or more, more preferably 5% or more, and most preferably 6% or more. The difference in crimp percentage of less than 4% is not desirable because the air permeability under high pressures cannot be made large. The degree of intermingle of unwoven yarn (yarn taken out from woven fabric) in warp and/or weft is preferably 8 times/m or less, and more preferably 6 times/m or less. The degree of intermingles of unwoven yarn higher than 8 times/m is not desirable because the air permeability is high.
The air permeability under 50 kPa differential pressure in the present invention is 2.5 L/cm
2
/min. or less, preferably 2 L/cm
2
/min. or less, and most preferably 1.5 L/cm
2
/min. or less. If the air permeability under 50 kPa differential pressure exceeds 2.5 L/cm
2
/min., the mechanical property in the expanded state is not satisfactory.
The air permeability index under 50 kPa differential pressure in the present invention is preferably 1.2 or more, more preferably 1.3 or more, and most preferably 1.5 or more, with 1.8 or more being particularly preferred. The air permeability index of less than 1.2 is not desirable because collision to the passenger under high pressures at the time of expansion of the air bag is not sufficiently reduced.
The degree of intermingle of raw yarn is preferably 10 to 30 times/m, and more preferably 15 to 25 times/m. The degree of intermingle of less than 10 times/m is not desirable because fluff will generate to deteriorate the weaving efficiency and drawbacks due to the fluff increase to deteriorate the quality. On the other hand, the degree of intermingle of more than 30 times/m is not desirable because the remaining degree of intermingle of yarns constituting the fabric after weaving is large, so that low air permeability cannot be obtained, causing decrease of the strength.
The cover factor in the present invention is preferably 1800 to 2400, and more preferably 1900 to 2300. The cover factor of less than 1800 is not desirable because low air permeability cannot be obtained. The cover factor of more than 2400 is not desirable because troubles at the time of weaving increase to deteriorate the productivity.
It is necessary that the shrinkage percentage by boiling water of the thermoplastic fiber used in the present invention is 5 to 15%. If the shrinkage percentage by boiling water is less than 5%, low air permeability cannot be obtained, while on the other hand, if the shrinkage percentage by boiling water is more than 15%, the thickness of fabric after shrinkage is large, so that the compactness will be lost.
While the value of the shrinkage percentage by boiling water is preferably 5 to 15%, 8 to 12% is more preferred. While the temperature of heat treatment in the present invention is not particularly specified, heat treatment is usually performed at 100 to 200° C. It is preferred that heat treatment is performed at 160° C. or less from the viewpoint of achieving low air permeability. While the treatment is performed by heat setter, boiling water bath and the like not specified means, it is possible to use a processing machine enabling about 0 to 15% of over feed in the vertical and horizontal directions. The over feed at the time of boiling water treatment is more than 3 times, more preferably 5 times, and most preferably 10 times the over feed at the time of dry setting. In the boiling water treatment, it is not necessarily to use
Ban Kaoru
Kitamura Mamoru
Leydig , Voit & Mayer, Ltd.
Singh Arti R.
Toyo Boseki Kabushiki Kaisha
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