CA2187586C

CA2187586C - Flame-retardant fabrics containing phosphorus-modified polyester fibers, airbags made therefrom and use thereof

Info

Publication number: CA2187586C
Application number: CA002187586A
Authority: CA
Inventors: Burkhard Bonigk
Original assignee: Invista Technologies SARL Luxembourg
Current assignee: Invista Technologies SARL Luxembourg
Priority date: 1995-10-11
Filing date: 1996-10-10
Publication date: 2004-12-21
Anticipated expiration: 2016-10-10
Also published as: EP0773140A1; BR9605036A; CA2187586A1; CN1046562C; CN1157347A; EP0773140B1; MX9604728A; KR100487990B1; KR970021404A; DE19537699A1; DE59606303D1; JPH09111587A

Abstract

Uncoated fabrics are described which have a gas permeability of less than or equal to 80 dm3 of air per minute per square decimeter at a pressure drop of 500 Pa (measured as specified in DIN 53 887) and which have at least two thread systems of parallel threads made of high-tenacity polyester filament yarns and having a yarn linear density of 150 to 700 dtex, and having an individual filament linear density of less than or equal to 7 dtex. In the fabrics, the polyester is a phosphorus-modified copolyester which contains a bifunctional phosphorus compound in an amount of 0.1 to 5% by weight, based on the amount of phosphorus, in the polymer chain.
Flame-retardant and uncoated airbags may be manufactured from fabrics of this type.

Description

Hoechst Trevira GmbH & Co. KG HOE 95/T021 Dr. BR/St Description Flame-retardant fabrics containing phosphorus-modified polyester fibers, airbags made therefrom and use thereof The present invention relates to flame-retardant fabrics having high gas tightness, airbags comprising these fabrics and to the use of these fabrics for manufacturing airbags.
Airbags are inflated explosively in the event of an accident and are intended to protect the occupants of vehicles, in particular automobile drivers, against impact injuries. Airbags are manufactured in part from gas-impermeable, coated fabrics, which, on one side of the bag, include a gas-permeable filter fabric or filter fabric segment or an opening.
In the development of textile safety components for the automobile, strength is of major importance. However, if in the event of an accident the airbag is deployed, this remains in the interior of the vehicle as relatively large surface areas of textile. In the event of fire this represents a hazard to the occupants, similarly to as is known from curtains in the residential sector.
JP-A-91-167,312 discloses fire-retardant polyester fibers for manufacturing fabrics, which themselves are suitable for manufacturing airbags. The disclosure in this publication only describes airbags made of coated fabrics. Fabrics of this type do not need to be particularly gas-tight from the manufacturer, since the gas-tightness is mainly achieved by the coating.
Conclusions about the fire behavior of uncoated fabrics cannot be readily drawn from the fire behavior of coated fabrics. Therefore, no conclusions can be drawn from JP-A-91-167,312 that the fire behavior of fabrics which are uncoated and spaced so as to be gas tight. According to the single example in this publication, the linear density of the yarns used is dtex 833 f 96, the individual filament linear density being therefore 8.7 dtex.
It has already been proposed to use uncoated fabrics for manufacturing airbags, for example in EP-A-453,678, in EP-B-442,373 or in EP-B-509,399. These fabrics, because of their fine yarn linear density and filament linear density are subject to a greater flame hazard than fabrics made from coarser yarn and filament linear densities. These publications give no references to the use of flame-retardant fabrics for manufacturing airbags.
EP-A-661,393 discloses high-tenacity and flame-retardant polyester yarns.
This publication gives no references to the use of these yarns for manufacturing flame-retardant and tightly spaced fabrics.
In view of the increasing safety requirements in motor vehicles, there is still a need for fabrics which are flame-retardant, usable uncoated and gas tight, which themselves can be used in the manufacture of airbags.
It is therefore the object of the present invention to provide fabrics for manufacturing airbags, which fabrics have the necessary safety properties of known fabrics and, moreover, in addition have fire-retardant properties.
In the airbag, this is of importance, depending on the construction, for the gas-tight and the gas-permeable part.
It has now surprisingly been found that fabrics of this type may be manufactured by using fire-retardant and phosphorus-modified polyester filaments.
The invention relates to uncoated fabrics which have a gas permeability of less than or equal to 80 dm3 of air per minute per square decimeter at a pressure drop of 500 Pa (measured as specified in DIN 53 887), and which have at least two thread systems of parallel threads made of high-tenacity polyester filament yarns and having a yarn linear density of 150 to 700 dtex, preferably 220 to 550 dtex, and having an individual filament linear density of less than or equal to 7, preferably of less than or equal to 4 dtex.
In the fabrics of the invention, the polyester is a phosphorus-modified copolyester which contains a bifunctional phosphorus compound in an amount of 0.1 to 5% by weight, preferably 0.2 to 0.8% by weight, based on the amount of phosphorus, in the polymer chain.
The fabrics of the invention can comprise a relatively small proportion, or can consist completely, of the above defined high-tenacity and phosphorus-modified filament yarns. Thus, it is possible, for example, to make up only one of the thread systems making up the fabrics of the invention entirely or only partly from these yarns. Those skilled in the art can determine, on the basis of routine experiments, the amount necessary in the individual case of the above defined high-tenacity and phosphorus-modified filament yarns, for example taking as a basis the desired strength of the fabric.
Use of the phosphorus-modified polyester fibers increases the flame-retardancy of the fabrics manufactured therefrom. Flame-retardant fabric in the context of this description is taken to mean a loomstate fabric which has, in the flammability testing as specified in DIN 4102/B2, a total burning time which is shorter by at least the factor 5, preferably by the factor 10, than that of a comparable loomstate fabric of non-phosphorus-modified polyester and which does not afterburn after a flame is applied for 3 and 15 seconds as specified in DIN 54336 or for 3 seconds as specified in DIN
54333.
In addition to the above defined high-tenacity and phosphorus-modified filament yarns, some of the yarns making up the fabrics can comprise non-phosphorus-modified and high-tenacity filament yarns.
Preferably, at least one direction, e.g. the weft direction or the warp direction, of the fabric of the invention is made up completely of the above defined high-tenacity and phosphorus-modified filament yarns; particularly preferably, both directions are made up of filament yarns of this type.
The fabrics of the invention can consist of two or more thread systems;
preferably, two thread systems are provided (warp and weft yarn sheets).
Very particularly preferably, fabrics are used which consist of two thread systems, each of which comprises at least 95% of the above defined high-tenacity and phosphorus-modified filament yarns.
The gas permeability of the fabrics of the invention can be varied within wide limits.
In the so-called gas-tight part, the gas permeability is customarily less than or equal to 12 dm3 of air per minute per square decimeter at a pressure drop of 500 Pa (measured as specified in DIN 53 887). In the so-called gas-permeable part, the gas permeability is customarily 12 to 80 dm3 of air per minute per square decimeter at a pressure drop of 500 Pa (measured as specified in DIN 53887).
The gas permeability is measured as described in DIN 53 887 on a fabric having a measurement area of 100 cm2 and at a pressure drop (measurement pressure) of 500 Pa.
Particular preference is given to uncoated fabrics as defined above whose high-tenacity polyester yarns have a tenacity of more than 55 cN/tex, and a breaking elongation of more than 15%.

The breaking force and the breaking elongation of the polyester yarns used were measured as described in DIN 53 830, part 1.
Particular preference is given to uncoated fabrics as defined above whose 5 high-tenacity polyester yarns have a heat shrinkage at 200°C of less than 9%.
The heat shrinkage (hot-air shrinkage) of the polyester yarns used is measured as described in DIN 53 866, part 3, at a temperature of 200°C
on free-hanging yarn samples with a treatment time of 15 minutes. 10 m hanks at a reel tension of 0.5 cN/tex are used.
Particular preference is given to uncoated fabrics as defined above whose high-tenacity polyester yarns are free of sizing.
The uncoated fabrics of the invention preferably have a plain weave, a ripstop weave, a cross twill weave, a crepe weave or a modified huckaback weave.
The fabric construction is determined as specified in DIN 53 853.
Fabrics having these weaves are known per se, for example from EP-B-442,272 and EP-B-509,399.
Preferably, the uncoated fabrics of the invention have a mass per unit area of less than 300 g/m2, preferably less than 240 g/m2, and a fabric thickness of less than 0.45 mm, preferably less than 0.35 mm.
The mass per unit area of the fabrics of the invention is measured as specified in DIN 53 854; the thickness of the fabrics of the invention is measured as described in DIN 53 855, part 1 (measurement area 10 cm2;

measurement pressure 50 cN/cmZ).
The breaking force of the uncoated fabrics of the invention is preferably greater than 220 daN; their breaking elongation is preferably greater than 25%, each of these two values being measured on a 5 cm-wide fabric strip.
The high-tenacity filament yarns used in the fabrics of the invention consist of polyester filaments which are made up of a phosphorus-modified copolyester.
The copolyester can be any type of spinnable copolymer having repeating ester groups, provided it contains in the polymer chain a bifunctional phosphorus compound in the amount specified above.
Preferably, high-tenacity filaments of phosphorus-modified copolyesters are used which contain the repeating structural units of the formula I
-O-OC-Ar'-CO-O-R'- (I), and which have in the polymer chain components of the formula II
O O
-O-P-RZ-C- (I I), in which Ar' is a divalent aromatic radical, R' is a divalent aliphatic or cycloaliphatic radical, R2 is a divalent aliphatic, cycloaliphatic, aromatic or araliphatic radical, and R3 is a monovalent aliphatic, cycloaliphatic, aromatic or araliphatic radical.

Particularly preferably, modified polyesters of the above indicated type are used in which Ar' is phenylene or naphthylene, in particular 1,4-phenylene or 2,6-naphthylene.
Likewise particularly preferably, polyesters of the above indicated type are used in which R' is a radical of the formula -C~H2~-, in which n is an integer between 2 and 6, in particular ethylene, or a radical derived from cyclohexanedimethanol.
Likewise particularly preferably, modified polyesters of the above indicated type are used in which RZ is a radical of the formula -CmH2m-, in which m is an integer between 2 and 10, or a cyclic alkanediyl radical having 4 to 8, preferably 6, carbon atoms, and R3 is C,-Csalkyl, cyclohexyl, phenyl, or benzyl.
If any radicals in the structural formulae defined above are divalent aliphatic radicals, this is to be understood as including branched and, in particular, straight-chain alkylene, for example alkylene having two to twenty, preferably two to eight, carbon atoms. Examples of radicals of this type are ethane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl or octane-1,8-diyl.
If any radicals in the structural formulae defined above are divalent cycloaliphatic radicals, this is to be understood as including groups which contain carbocyclic radicals having five to eight, preferably six, ring carbon atoms. Examples of radicals of this type are cyclohexane-1,4-diyl or the group -CH2 C6H,o CH2 .
If any radicals in the structural formulae defined above are divalent aromatic radicals, these are heterocyclic aromatic radicals, which can be mononuclear or polynuclear, or, in particular, mononuclear or polynuclear aromatic hydrocarbons. In the case of heterocyclic aromatic radicals, these have, in particular, one or two oxygen, nitrogen or sulfur atoms in the aromatic nucleus.
Polynuclear aromatic radicals can be condensed with one another or can be joined to one another via C-C bonds or via bridging groups, such as -O-, -S-, -CO- or -CO-NH- groups.
The valence bonds of the divalent aromatic radicals can be in the para or comparable coaxial or parallel position to one another, or else in the meta or comparable angled position to one another.
The valence bonds which are in coaxial position or a position parallel to one another are oriented in opposite directions. An example of coaxial bonds oriented in opposite directions are the biphenyl-4,4'-diyl bonds. An example of parallel bonds oriented in opposite directions are the 1,5-naphthylene or-2,6-naphthylene bonds, whereas the 1,8-naphthylene bonds are oriented in the same direction in parallel.
Examples of preferred divalent aromatic radicals whose valence bonds are in the para or comparable coaxial or parallel position to one another are mononuclear aromatic radicals having free valencies in the para position to one another, in particular 1,4-phenylene or dinuclear condensed aromatic radicals having parallel bonds oriented in opposite directions, in particular 1,4-, 1,5- and 2,6-naphthylene, or dinuclear aromatic radicals linked via a C-C bond having coaxial bonds oriented in opposite directions, in particular 4,4'-biphenylene.
Examples of preferred divalent aromatic radicals whose valence bonds are in the meta or comparable angled position to one another are mononuclear aromatic radicals having free valencies in the meta position to one another, in particular 1,3-phenylene or dinuclear condensed aromatic radicals having bonds oriented at an angle to one another, in particular 1,6- and 2,7-naphthylene, or dinuclear aromatic radicals linked via a C-C bond having bonds oriented at an angle to one another, in particular 3,4'-biphenylene.
If any radicals are divalent araliphatic radicals, this is to be understood as including groups which contain one or more divalent aromatic radicals which are combined with an alkylene radical via one or both valencies. A
preferred example of a radical of this type is the group -C6H4 CH2 .
If any radicals are monovalent aliphatic radicals, these are to be understood as including branched and, in particular, straight-chain alkyl, for example alkyl having one to six carbon atoms, in particular methyl.
If any radicals are monovalent cycloaliphatic radicals, these are to be understood as including groups which contain carbocyclic radicals having five to eight, preferably six, ring carbon atoms. An example of a radical of this type is cyclohexyl.
If any radicals are monovalent aromatic radicals, these are heterocyclic aromatic radicals, which can be mononuclear or polynuclear, or, in particular, mononuclear or polynuclear aromatic hydrocarbon radicals. In the case of heterocyclic aromatic radicals, these have, in particular, one or two oxygen, nitrogen or sulfur atoms in the aromatic nucleus. An example of a radical of this type is phenyl or naphthyl.
If any radicals are monovalent araliphatic radicals, these are to be understood as including groups which contain one or more aromatic radicals which are combined with an alkylene radical via one valence. A
preferred example of a radical of this type is the benzyl group.
All these aliphatic, cycloaliphatic, aromatic or araliphatic radicals can be substituted with inert groups. These are to be understood as including substituents which do not adversely affect the contemplated application.

Examples of such substituents are alkyl, alkoxy or halogen.
If any radicals are halogen, these are, for example, fluorine, bromine or, in particular, chlorine.

Particularly preferably, the filament yarns used according to the invention are filament yarns made of phosphorus-modified polyethylene terephthalate).
10 The high-tenacity filament yarns used in the fabrics of the invention can be made up of modified polyesters which customarily have an intrinsic viscosity of at least 0.5 dl/g, preferably 0.6 to 1.5 dl/g. The intrinsic viscosity is measured in a solution of the polyester in dichloroacetic acid at 25°C.
The high-tenacity filament yarns used according to the invention customarily have yarn linear densities of 150 to 700 dtex, preferably 220 to 550 dtex.
The single-fiber linear density of the filaments in the high-tenacity filament yarns used according to the invention customarily varies in the range of less than or equal to 7 dtex, preferably less than or equal to 5 dtex, in particular 2 to 4 dtex.
The cross sections of the filaments in the high-tenacity filament yarns according to the invention used can be of any shape; for example elliptical, bilobal or multilobal, ribbon-like or, preferably, round.
The high-tenacity filament yarns used according to the invention made of phosphorus-modified polyesters are likewise known per se as reinforcement and coating substrates, for example from EP-A-661,393 .

The thermoplastic polymers are prepared by processes known per se by polycondensation of the corresponding bifunctional monomer components, as is described, for example, in the abovementioned EP-A-661,393.
The high-tenacity filaments can be produced by melt spinning processes known per se, such as are described, for example, in the abovementioned EP-A-661,393.
The fabrics of the invention can be manufactured by weaving techniques known per se, as has been described, for example, in the abovementioned EP-B-442,272 and EP-B-509,399 .
If an air permeability as low as possible is desired - as is desired, in particular, for the curved surface area of the airbag, the fabric should have the tightest possible fabric construction - for the chosen yarn linear density and the chosen fabric structure - ie. the fabric, preferably in a plain or ripstop structure, is to receive the highest possible thread count in weaving per unit length in the warp and weft direction.
The thread counts of at least one of the thread systems of the fabrics of the invention are customarily at least 15 threads per centimeter, preferably at least 20 threads per centimeter.
The invention likewise relates to airbags containing an uncoated and flame-retardant fabric as defined above.
Fabrics for this application preferably have a burst strength according to Mullen of greater than or equal to 3500 kPa, a breaking force of greater than or equal to 1300 N, for each 5 cm of fabric width, a tear propagation resistance, measured by the trousers tear test, of greater than or equal to 100 N, and a breaking elongation of greater than or equal to 20%

The properties listed are measured in this case as follows:
Burst strength according to Mullen: Federal Test Method Standard No: 191A, Method 5122 Breaking force: as specified in DIN 53 857, part 1 Tear propagation resistance (trousers tear test): as described in DIN 53 356 (sample size 150 * 200 mm tubular; Evaluation as specified in DIN 53539, B) Breaking elongation: as specified in DIN 53 857, part 1 The invention further relates to the use of the above defined fabrics for manufacturing airbags.

Claims

1. An uncoated fabric which has a gas permeability of less than or equal to 80 dm3 of air per minute per square decimeter at a pressure drop of 500 Pa (measured as specified in DIN 53 887), which has two thread systems of parallel threads, each system comprises at least 95% of high tenacity polyester filament yarns, having a linear density of 150 to 700 dtex, and having an individual filament linear density of less than or equal to 7 dtex, wherein the polyester is a phosphorus-modified copolyester which contains a bifunctional phosphorus compound in an amount of 0.1 to 5% by weight, based on the amount of phosphorus, in the polymer chain.

2. The uncoated fabric as claimed in claim 1, wherein the bifunctional phosphorus compound is in an amount of 0.2 to 0.8% by weight, based on the amount of phosphorus in the polymer chain.

3. The uncoated fabric as claimed in claim 1, wherein its gas permeability is 12 to 80 dm3 of air per minute per square decimeter at a pressure drop of 500 Pa (measured as specified in DIN 53887).

4. The uncoated fabric as claimed in claim 1, wherein its gas permeability is less than or equal to 12 dm3 of air per minute per square decimeter at a pressure drop of 500 Pa (measured as specified in DIN 53887).

5. The uncoated fabric as claimed in claim 1, wherein the high-tenacity polyester yarn has a tenacity of more than 55 cN/tex, and a breaking elongation of more than 15%.

6. The uncoated fabric as claimed in claim 1, wherein the high-tenacity polyester yarn has a heat shrinkage at 200°C of less than 9%.

7. The uncoated fabric as claimed in claim 1, wherein the high-tenacity polyester yarn is free of sizing.

8. The uncoated fabric as claimed in claim 1, wherein the uncoated fabric is selected from the group consisting of a plain weave, a ripstop weave, a cross twill weave, a crepe weave and a modified huckaback weave.

9. The uncoated fabric as claimed in claim 1, wherein this has a mass per unit area of less than 300 g/m2 and a fabric thickness of less than 0.45 mm.

10. The uncoated fabric as claimed in claim 1, wherein this has a breaking force greater than 220 daN and a breaking elongation greater than 25%, both measured on a 5 cm-wide fabric strip.

11. The uncoated fabric as claimed in claim 1, wherein the phosphorus modified copolyester is a polyester which contains the repeating structural units of the formula I
-O-OC-Ar1-CO-O-R1- (I), and which has in the polymer chain components of the formula II
in which Ar1 is selected from the group consisting of a divalent mononuclear and a divalent polynuclear aromatic radical, R1 is selected from the group consisting of a divalent aliphatic and a divalent cycloaliphatic radical, R2 is selected from the group consisting of a divalent aliphatic, a divalent cycloaliphatic, a divalent aromatic and a divalent araliphatic radical, and R3 is selected from the group consisting of a monovalent aliphatic, a monovalent cycloaliphatic, a monovalent aromatic and a monovalent araliphatic radical.

12. The uncoated fabric as claimed in claim 11, wherein Ar1 is selected from the group consisting of phenylene and naphthylene.

13. The uncoated fabric as claimed in claim 11, wherein Ar1 is selected from the group consisting of 1,4-phenylene or 2,6-naphthylene.

14. The uncoated fabric as claimed in claim 11, wherein R1 is selected from the group consisting of a radical of the formula -C n H2n,-, in which n is an integer between 2 and 6, and a radical derived from cyclohexanedimethanol.

15. The uncoated fabric as claimed in claim 14 wherein the R1 radical of the formula C n H2n is ethylene.

16. The uncoated fabric as claimed in claim 11, wherein R2 is selected from the group consisting of a radical of the formula -C m H2m-, in which m is an integer between 2 and 10, and a cyclic alkanediyl radical having 4 to 8 carbon atoms, and R3 is selected from the group consisting of C1-C6alkyl, cyclohexyl, phenyl, and benzyl.

17. The uncoated fabric as claimed in claim 16, wherein the cyclic alkanediyl radical has 6 carbon atoms.

18. An airbag containing an uncoated fabric as claimed in claim 1.

19. Use of the fabric as claimed in claim 1 for manufacturing airbags.