JP3156849B2 - Base fabric for airbag - Google Patents

Description

The present invention relates to a base fabric for an air bag. More lightweight and flexible, excellent dimensional stability and shrinkage,
The present invention relates to an airbag base fabric having excellent mechanical properties.

[Related Art] In recent years, as a safety device for protecting an occupant of an automobile, mounting of an airbag is rapidly progressing.

Normally, an airbag is stored in such a manner that its bag-shaped body is folded for a long time in a steering wheel, an instrument panel, or the like. Then, in the event of an accident, the impact of the collision is sensed by a sensor, and the explosive gas from the inflator causes the bag to expand and inflate, thereby preventing the occupant from moving during the collision to ensure occupant safety.

Therefore, as a function required of the airbag, first, as a necessary property in the event of an emergency, the strength of the base fabric that can withstand instantaneous inflation, especially the tensile strength, tearing strength, bursting strength, etc. are high, That the base fabric has good air shielding properties to enable instantaneous inflation, and that the base fabric has good inflation responsiveness, that the inflated airbag has a large shock absorption energy after hitting the occupant,
Further, it has heat resistance to high-temperature gas generated from the inflator.

In addition, the characteristics that are required at normal times include that they are lightweight, flexible, have a small storage volume, have no dimensional change, and are resistant to climatic changes in the storage container because they are stored in a narrow place for a long time. Not deteriorate.

Good control of the air shielding properties of the airbag base fabric,
In order to impart heat resistance, a method of coating the surface of the base fabric with polychloroprene rubber, silicone rubber, or the like is generally used. In recent years, airbags that control the air shielding property by devising a woven fabric structure such as a high-density woven fabric, and that do not require a high heat resistance of a base fabric by using a low-temperature inflator have been put into practical use.

On the other hand, as described above, it is desired that the base cloth has good foldability while maintaining various properties necessary in an emergency, such as softening with a silicone rubber coat, and further non-coat base cloth. And so on. As a proposal for improvement from fibers, there has also been proposed a raw yarn which has excellent mechanical properties, is flexible, has excellent foldability, and can reduce the storage volume. For example, Japanese Patent Application Laid-Open No. Sho 64-41438 discloses an airbag base fabric comprising a yarn having a strength of 8.5 g / d or more and a single denier of 3 denier or less.

[Problem to be Solved by the Invention] The technology disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 64-41438 is
For the purpose of making the base fabric flexible, excellent in foldability, and reducing the storage volume, a single fiber denier of the constituent fibers is 3 denier or less. Certainly, according to this technique, although the performance of the base fabric for an air bag is satisfactory, it is shown in Examples 1 to 3 of the publication.
When a total denier of nylon 66 is 840 denier, the denier of single yarn is 3 denier or less, yarn spots at the time of spinning, yarn breakage at the time of drawing, single yarn breakage, and fluff occur frequently. In addition, the efficiency of weaving is deteriorated, and the obtained airbag base fabric has drawbacks such as unevenness due to fluffing, warps, and wefts, and has a problem that only unsatisfactory quality can be obtained.

In general, if the single yarn denier is thin and the number of filaments is large, yarn spots and single yarn collisions are likely to occur due to variation in polymer viscosity during the spinning process, and the single yarn is cut in the drawing process due to low strength per single yarn. The above phenomenon occurs because fluff is easily generated.

Conventionally, its flexibility as a base yarn for airbag fabric,
Nylon 66 fiber has been mainly used in terms of mechanical properties and adhesiveness to rubber to be coated. However, during storage of the base fabric in the air bag storage box for a long period of time, there have been problems that the dimensions change during that time, and that the expansion responsiveness of the base fabric upon impact is slightly inferior. As a means to solve the problem, use of a fiber having high elastic modulus and low shrinkage, for example, polyester fiber, is considered. Has a problem that it becomes defective.

Therefore, the present invention solves the above-mentioned problems of the prior art, and provides an airbag base fabric which is flexible, excellent in dimensional stability and excellent in storability without impairing the mechanical properties of the airbag.

[Means and Actions for Solving the Problems] In order to achieve the above object, the constitution of the present invention is as follows: (1) A polyester having substantially an ethylene terephthalate unit as a main component and a polyamide as a sheath component. A composite fiber having a core-in-sheath composite structure, wherein the ratio of the core component to the core component and the sheath component is 20 to 90% by weight.
And a composite fiber yarn having the following characteristics (A) and (B) as warp and / or weft:

(A) Dry heat shrinkage stress at 75 ° C. ≦ 0.10 g / d (B) Birefringence of sheath portion ≦ 56 × 10 ⁻³ (2) It has the following characteristics (a) to (d) The base fabric for an airbag according to the above (1).

(A) Tensile strength ≧ 180 kg / 3 cm (b) Tear strength ≧ 18 kg / 2.54 cm (c) Burst strength ≧ 45 kg / mm ² (d) Flexibility ≦ 80 mm measured by the cantilever method.

The polyester which is a core component of the composite fiber used for the base fabric for an air bag of the present invention is preferably a polyester substantially comprising polyethylene terephthalate units. The polyethylene terephthalate polymer may contain a copolymer component that does not substantially lower the physical and chemical properties of the polymer, for example, less than 10%. The copolymerization component may include a dicarboxylic acid such as isophthalic acid, naphthalenedicarboxylic acid, and diphenyldicarboxylic acid, and a diol component such as ethylene oxide, propylene glycol, and butylene glycol.

The intrinsic viscosity [η] of the polyethylene terephthalate portion of the core component of the composite fiber for an airbag base fabric of the present invention has a high degree of polymerization of at least 0.7, preferably at least 0.8. When the intrinsic viscosity [η] is less than 0.7, good mechanical properties aimed at by the present invention, that is, high strength of the base cloth that can withstand instantaneous expansion, particularly high tensile strength, high tear strength, high burst strength,
Also, large impact absorption energy or the like after the inflated airbag hits the occupant cannot be obtained.

On the other hand, the polyamide sheath component is composed of ordinary polyamides such as polycapramid, polyhexamethylene adipamide, polytetramethylene adipamide, polyhexamethylene sebacamide, and polyhexamethylene dodecamide. Polymers are preferred.

Like the polyester core component, the polyamide sheath component polymer requires a high degree of polymerization in order to obtain an airbag base fabric having good mechanical properties, and has a sulfuric acid relative viscosity of 2.8 or more, preferably 3.0 or more. It is preferable to add a copper salt and other organic and inorganic compounds to the polyamide sheath component in order to improve heat resistance and weather resistance. In particular, copper salts such as copper iodide, copper acetate, copper chloride and copper stearate are used as copper in an amount of 30 to 500 ppm, and potassium iodide, sodium iodide and 0.01 to 0.5% by weight of an alkali metal halide such as potassium bromide, and It is preferable to contain 0.01 to 0.1% by weight of an organic or inorganic phosphorus compound.

The proportion of the polyester core component in the composite fiber for an airbag base fabric of the present invention is 20 to 90% by weight. Polyester component
If the content is less than 20% by weight, it is impossible to obtain a modulus for improving the expansion responsiveness of the base fabric at the time of collision and good dimensional stability during long-term storage in a storage box as a target fiber. On the other hand, when the polyester core component occupies 90% by weight or more, the fibers are hard and the foldability as an airbag deteriorates, which is not preferable as a fiber for a base fabric for an airbag.

The composite fiber used for the airbag base fabric of the present invention is characterized by a low orientation of the polyamide sheath component. That is, the birefringence of the polyamide sheath component is 56 × 10 ⁻³ or less, preferably 55 ×
The orientation is as low as 10 ^-3 or less. 56x birefringence
If it exceeds 10 ^-3 , fluff is likely to occur, and the fibers are hard, so that the foldability as an airbag is poor, and the strength of the base fabric is reduced by bending, which is not preferable as a fiber for a base fabric for an airbag. The measurement of the sheath birefringence of the conjugate fiber according to the airbag base fabric of the present invention is measured by a transmission interference microscope.

The composite fiber used for the airbag base fabric of the present invention is
It is characterized by low drying shrinkage stress at 75 ° C. That is, the dry heat shrinkage stress of the conjugate fiber at 75 ° C. is 0.10 g / d or less, preferably 0.09 g / d or less. If the dry heat shrinkage stress at 75 ° C exceeds 0.10 g / d, fluff is likely to occur, and the dimensional stability as a base fabric is deteriorated,
Further, the strength of the base fabric is reduced by bending, which is not preferable as a fiber for a base fabric for an airbag.

The composite fiber yarn according to the airbag base fabric of the present invention is 15
It is from 0 to 1000 denier, preferably from 210 to 840 denier. The single yarn fineness is 1 denier or more, preferably 3 denier or more. The strength of the fiber yarn is 8 g / d or more, preferably 8.
High strength of 5-12 g / d.

The airbag base fabric of the present invention includes, for example, a woven fabric, a knitted fabric, a laminate thereof, and a sheet strip. However, an isotropic woven fabric such as taffeta is preferable from the overall performance of the airbag base fabric. The density of the woven fabric of the airbag base fabric is preferably a high-density woven fabric having a cover factor (K) of 1500 or more, which is obtained from the product of the square root of the fiber thread and the following formula.

In addition, the airbag fabric of the present invention is most preferably configured as an airbag with the fabric alone in order to effectively exhibit the characteristics of the composite fiber according to the present invention as basic performance. For the purpose of controlling, imparting heat resistance, reinforcing a sewn portion, or the like, an elastomer can be used as a secondary coating on the entire surface or a part. As the elastomer, for example, chloroprene rubber, silicone rubber, urethane resin, or the like is used.

The composite fiber used as the base yarn of the base fabric for an airbag of the present invention is produced by the following method.

As the polyester core component, a polymer substantially consisting of polyethylene terephthalate having an intrinsic viscosity [η] of 0.75 or more, usually 0.85 or more is used. As the polyamide sheath component polymer, a polymer having a high polymerization degree of 2.8 or more in sulfuric acid relative viscosity, usually 3.0 or more is used.

It is preferable to use two extruder-type spinning machines for melt spinning of the polymer. The polyester and polyamide polymers melted by the respective extruders are guided to a composite spinning pack, and are spun through a composite spinneret as a composite fiber having polyester in the core and polyamide in the sheath.

After spinning, the filament is placed immediately below the base and has a length of 20-50.
After passing through a high-temperature atmosphere heated to 0 mm and a temperature of 200 ° C. to 400 ° C., it is cooled and solidified by cold air, then applied with an oil agent, and then taken up by a take-up roll.

The spinning speed is 4000 m / min or less, preferably 200 to 3
000 m / min, more preferably 300 to 2000 m / min. 4000m /
When the length exceeds 200 m / min, it is difficult to stably produce a high-strength yarn of 8 g / d or more, while when it is less than 200 m / min, the production efficiency of the yarn is low and disadvantageous.

Further, control of the high-temperature atmosphere immediately below the base is particularly necessary to increase the uniformity between the individual yarns constituting the yarn, whereby a yarn with less fluff is obtained, and a high-quality airbag base fabric is obtained. can get. The high-temperature atmosphere is preferably an inert gas such as nitrogen gas or superheated steam from the viewpoint of fiber uniformity.

The drawn undrawn yarn is usually drawn continuously, but may be drawn once and then drawn in another step.

Next, the drawn undrawn yarn is 200 ° C. or higher, preferably 2 ° C.
It is hot stretched at a temperature of 10 to 250 ° C. Stretching is preferably performed in two or more stages, and the stretching ratio is 2 to 7 times, preferably 3 to 6 times.

The base fabric for an airbag using the composite fiber obtained by the above method has a high tensile strength of 180 kg / 3 cm or more, a tear strength of 18 kg / 2.45 cm or more, and a breaking strength of 45 kg / mm ² or more. And the flexibility measured with a cantilever is 60mm
It was flexible as follows, had good dimensional stability, and was excellent in storage.

Next, the present invention will be described based on Examples, the present invention text, and the polymers, fibers, and fabric properties described in the Examples,
And the measuring method is as follows.

<Polymer Characteristics> (a) Intrinsic viscosity [η]: A polyethylene terephthalate chip sample was dissolved in an orthochlorophenol solution and measured at 25 ° C. using an Ostwald viscometer.

(B) Sulfuric acid relative viscosity ηr: Dissolve 0.25 g of nylon chip sample in 25 cc of 98% sulfuric acid,
It was measured at 25 ° C. using an Ostwald viscometer.

<Characteristics of composite fiber> (c) Tensile strength and tensile elongation: According to the definition and measurement method of JIS L-1017.

(D) Dry heat shrinkage stress Sample length 25cm, initial load 0.05g / d, heating rate 10% / min 2
The temperature is raised from 5 ° C, and the shrinkage stress at 75 ° C is measured.

(E) Birefringence: Using a transmission quantitative interference microscope manufactured by Carl Zeiss Jena (Germany), the average birefringence observed from the side of the fiber filament by the interference fringe method was determined. Only the polyamide fiber portion was measured at 2 μ intervals from the fiber surface to the center.

<Characteristics of base fabric> (f) Tensile strength: JIS K-6328 (strip method), sample width 3cm
Was measured.

(G) Tear strength: JIS K-6328 (trabesoid method), sample width
Measured at 2.54 cm.

(H) Burst strength: Conforms to JIS K-6328 (Mullen method).

(I) Flexibility: Measured with a sample width of 2 cm according to JIS L-1096 (45 ° C. cantilever method).

(D) Dimensional stability when wet: A base cloth 20cm x 20cm is used as a sample, left in a temperature and humidity controlled room at 20 ° C and 65% RH for 24 hours or more, and then placed in a 50 ° C and 95% RH constant temperature and humidity chamber. Treat for 10 hours. Immediately after the treatment, the unevenness state of the sample was visually observed.

[Examples-1 to 4 and Comparative Examples-1 to 5] Intrinsic viscosity [η] 1.23, carboxyl end group concentration 18.5 eq
/ 10 ⁶ g polyethylene terephthalate (PET) and copper iodide 0.02 wt% hexamethylene adipamide containing potassium iodide 0.1%: melting (N66 relative viscosity in sulfuric acid Itaaru3.77) in each extruder type spinning machine Then, the mixture was guided to a composite spinning pack, and was spun from a core-sheath composite spinneret as a composite fiber of polyethylene terephthalate on the core and polyamide on the sheath. The ratio of the core component and the sheath component was changed as shown in the table. The die used had a hole diameter of 0.3 mmφ and 72 holes. The polymer temperature was 295 ° C for polyethylene terephthalate and 290 ° C for polyamide, and the spin pack temperature was 300 ° C.
C. and spun. A 15 cm heating cylinder was attached immediately below the base, and the atmosphere was heated to 290 ° C. in the cylinder. The ambient temperature is an ambient temperature measured at a position 10 cm below the die surface and 1 cm away from the outermost yarn. Attach a 100cm long Uniflow chimney under the heating cylinder, and blow cold air at 20 ° C and 30m / min at right angles to the yarn.
Cooled and solidified. Then, after applying the oil agent, the film was taken up by a take-up roll at a spinning speed of 600 m / min, and then continuously stretched without winding up for one day. The film was stretched in two steps, heat-treated while giving 5% relaxation, and wound up. The stretching conditions were as follows: the take-up roll was 80 ° C, the first stretch roll was 190 ° C, and the second stretch roll was 240 ° C. A non-heated roll was provided after the second stretching roll, and the relaxation treatment was performed.
It was set to 65% and the total draw ratio was changed. The discharge amount was changed so that the fineness of the drawn yarn was 420 denier.

The obtained raw yarns are each warped, and as warp and weft,
Weaved in an air jet loom. Weft driving speed is
Performed at 800 rpm. The number of fluffs during aging and the number of times the air jet loom stopped due to fluff of the original yarn were measured.

Next, a silicone rubber solvent solution was applied to the woven fabric so as to have a solid content of about 70 g / m ^2, and the properties of the coated base fabric obtained by vulcanization were measured.

The production conditions of the yarn, the characteristics of the yarn, the number of warping fluff, the number of times the loom is stopped, and the characteristics of the coating base fabric are shown in the table. In the table, the dry heat shrinkage stress at 75 ° C. is indicated as dry heat shrinkage stress (75 ° C.).

In Comparative Examples 4 and 5, nylon 66 and polyethylene terephthalate were individually melt-spun, and the spinning conditions were substantially the same as above except for the single die.

95% by weight of core component to core component and sheath component
In Comparative Example 1, the base fabric was hard and the foldability was poor. Further, in Comparative Example 2 in which the ratio of the core component to the core component and the sheath component was 10% by weight, fluffing occurred during aging, the loom was stopped slightly during weaving, and the dimensional stability when the base fabric was wet was poor. In Comparative Example 3 in which the birefringence of the sheath portion was as high as 57.3 × 10 ⁻³ , fluffing occurred during aging, the loom was stopped frequently during weaving, the base fabric was hard, and only a poor-quality base fabric could be obtained. The base fabrics of the nylon and polyester single yarns of Comparative Examples 4 and 5 each had poor dimensional stability or flexibility. Examples 1 to 4 of the present invention
The base fabric had good weaving property, was soft without impairing the mechanical properties, was flexible, had excellent dimensional stability and storability, and had good quality.

[Effects of the Invention] According to the present invention, mechanical properties are improved, and
A base fabric for an air bag having excellent dimensional stability, heat resistance, and storability can be obtained. Further, by using the airbag base fabric of the present invention, the size and weight of the storage device can be reduced.

Further, since the base fabric of the present invention is flexible and has excellent dimensional stability, heat resistance and mechanical properties, it can be widely used as various coated base fabrics other than air bags.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI D03D 15/00 D03D 15/00 C

Claims (2)

(57) [Claims] 1. A composite fiber having a core-in-sheath composite structure in which a polyester having substantially an ethylene terephthalate unit as a main component and a polyamide as a sheath component are provided,
The ratio of the core component to the core component and the sheath component is 20 to 90.
A base fabric for an air bag, wherein a composite fiber yarn having the following characteristics (A) and (B) is used as a warp and / or a weft by weight. (A) Dry heat shrinkage stress at 75 ° C. ≦ 0.10 g / d (B) Birefringence of sheath portion ≦ 56 × 10 ⁻³ 2. The airbag fabric according to claim 1, wherein the fabric has the following characteristics (a) to (d). (A) Tensile strength ≧ 180kg / 3cm (b) Tear strength ≧ 18kg / 2.54cm (c) Burst strength ≧ 45kg / mm ² (d) Flexibility ≦ 80mm measured by cantilever method