JP2884769B2 - Base fabric for airbag - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a base fabric for an air bag, and more particularly, to a base fabric for an air bag that is lightweight, flexible, excellent in storage, and excellent in mechanical properties. It is about.

[Background Art] Mounting of airbags as a safety device for protecting occupants of automobiles is rapidly progressing.

This airbag is usually housed with its bag-shaped airbag body folded in the center of the steering wheel, and in the event of an automobile accident, the sensor detects a collision shock and the gas generated from the inflator. It is inflated and deployed to prevent the movement of the occupant in the event of a collision to ensure safety.

Therefore, the required function of the airbag is that the air permeability of the base cloth is small in order to inflate the airbag instantaneously, and the strength of the base cloth, especially tensile strength, tear strength, bursting, so that it can withstand instantaneous inflation The strength and the like are high, the energy which absorbs the impact after the inflated airbag hits the occupant is large, and the airbag has heat resistance against high-temperature gas generated from the inflator.

Since the airbag is usually stored in a narrow space such as a steering wheel or an instrument panel, there is a strong demand for a smaller storage volume. Therefore, airbag fabrics are as foldable as possible as long as the mechanical properties are satisfied, and efforts have been made to minimize the storage volume.

For example, the transition from polychloroprene rubber to silicone-based rubber is progressing in rubber-coated base fabrics, but this is because using silicone-based rubber requires a smaller amount of rubber coat to be applied, and a flexible rubber-coated base fabric can be obtained. It is.

However, it goes without saying that a non-coated base fabric is most advantageous in terms of softness, storability, and lightness of the base fabric for an air bag.

The conventional rubber-coated base fabric was advantageous in terms of controlling air permeability and heat resistance of the airbag, but the air permeability of the airbag can be controlled by a woven structure such as a high-density woven fabric. With the development of low-temperature inflators, the use of flame-retardant materials is not required.

However, with respect to heat resistance, there is a problem that the use of a non-coated base fabric with nylon 66 base fabric, which is commonly used, remains uneasy.

As a base fabric for an air bag, there has been proposed a yarn which is flexible while having excellent mechanical characteristics, has excellent folding characteristics, and can have a small storage volume. For example, the yarn described in JP-A-64-41438 has a strength of 8.5 g / d.
The above discloses an airbag base fabric using nylon 66 fiber having a single yarn denier of 3 denier or less.

[Problem to be Solved by the Invention] The technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 64-41438 discloses a single yarn denier for the purpose of making the base fabric for an airbag flexible and foldable, and reducing the storage volume. Uses a yarn of 3 denier or less.

Certainly, according to the above technology, the performance of the base fabric for an air bag is satisfactory, but nylon 66 fiber is used as the thread used for the base fabric, and the heat resistance is sufficient as a non-coated base fabric. Is not a problem.

Further, the rubber-coated base fabric has a problem that flexibility and foldability are limited, and light weight is not sufficient.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a flexible airbag base fabric without impairing the mechanical characteristics of the airbag, which has a small storage volume and a light weight. An air bag is realized.

[Means and Actions for Solving the Problems] To achieve the above object, the airbag base fabric of the present invention is used as a warp and / or a weft of an airbag base fabric.
90 mol% or more of the polymer constituent units are tetramethylene adipamide units, and the fibers are made of high polymerization degree polytetramethylene adipamide having a sulfuric acid relative viscosity of 3.5 or more. A polytetramethylene adipamide fiber yarn having a degree of 15% or more and a boiling water shrinkage of 5% or less is used. Further, the base fabric for an air bag preferably has the following mechanical properties and flexibility.

Tensile strength ≧ 180 kg / 3cm Tear strength ≧ 18 kg / 2.54 cm Flexibility (cantilever method) ≦ 70 mm The polytetramethylene adipamide fiber used for the airbag base fabric according to the present invention has 90 mol% of tetramethylene adipamide component. As described above, it is substantially composed of a tetramethylene adipamide unit, but particularly preferably contains 2 to 7% of a copolymer component.

As the copolymerization component, ε-caprolactam, aminocaproic acid, p-aminobenzoic acid, α-pyrrolidone, ω-
Nylon salts comprising an aminocarboxylic acid such as aminoundecane, a diamine component and a dicarboxylic acid component, for example, as a diamine component, hessamethylenediamine, octamethylenediamine, decamethylenediamine, p-phenylenediamine, m-phenylenediamine, cyclohexanediamine , P-xylylenediamine, m-xylylenediamine and the like, and as the dicarboxylic acid component, adipic acid, sebacic acid, terephthalic acid, isophthalic acid and the like can be used. When polymerized, a polytetramethylene adipamide fiber having excellent properties as a fiber used for a base fabric for an air bag aimed at by the present invention is obtained.

Further, the relative viscosity of sulfuric acid of the polytetramethylene adipamide fiber used for the base fabric for an air bag according to the present invention is 3.
High polymerization degree of 5 or more. If it is less than 3.5, the mechanical properties aimed at by the present invention, that is, the strength of the base cloth that can withstand instantaneous expansion, particularly impact strength, burst strength, tear strength, etc., and the impact after the inflated airbag hits the occupant, Does not satisfy the energy to be absorbed.

The polytetramethylene adipamide fiber yarn used for the airbag base fabric according to the present invention is preferably 150 to 100.
It is 0 denier, more preferably 210 to 840 denier.
The strength of the fiber yarn is 8.5 g / d or more, preferably 9.0 to 11.0 g / d
And high elongation, and the elongation is 15% or more, preferably 18% or more. In order to satisfy the mechanical properties required as a base fabric for an airbag, particularly, impact strength, tear strength, burst strength and absorbed energy, the above-mentioned fiber yarn needs to have strong elongation properties.

The polytetramethylene adipamide fiber used in the airbag fabric according to the present invention has a boiling water shrinkage of 5%.
Or less, preferably 3% or less, which is excellent in dimensional stability. For fibers having a boiling water shrinkage of 5% or more, it is difficult to stably control the air permeability of the base fabric due to heat shrinkage in a heat setting step when manufacturing an airbag base fabric.

The base fabric for an airbag of the present invention includes, for example, woven fabric, knitted fabric, a laminate thereof, a sheet-like material, and the like, and isotropic fabric is preferable in terms of overall performance as the base fabric for an airbag.

Normally, taffeta is used as the structure of the base fabric for an airbag, and the structure constituting density is a cover factor (K) obtained from the product of the square root of the fiber yarn fineness by the following formula.
It is preferable to use a high-density fabric of 1500 or more.

^{_{K = N W × D 1/2 +}} N F × D 1/2 N W: warp density (lines / inch) D ^1/2: warp denier N _F: weft density (lines / inch) D ^1/2: weft denier In the airbag fabric according to the present invention, it is most preferable to form the airbag with the fabric alone, in order to effectively exhibit the characteristics of the polyamide fiber as the fabric performance.

The airbag fabric according to the present invention is most excellent in flexibility, storability, and lightness when used without any coating.

However, the base fabric for an air bag according to the present invention can be sufficiently used as a coat base fabric in which an elastomer is secondarily coated on the entire surface or partially, and as the elastomer, for example, chloroprene rubber, silicone rubber, urethane Resin or the like is used.

Next, a method for producing a yarn used for the base fabric for an air bag according to the present invention, that is, a polytetramethylene adipamide fiber will be described in detail below.

The polytetramethylene adipamide fiber is a homopolymer composed of 90 mol% or more of tetramethylene adipamide units or a copolymer containing 10% or less of a copolymer component, and has a high polymerization degree having a sulfuric acid relative viscosity of 3.8 or more. Obtained by melt spinning the polymer. In order to obtain a fiber having a high strength and elongation suitable for the airbag base fabric of the present invention, the relative viscosity of sulfuric acid of the polytetramethylene adipamide fiber is 3.5 or more, preferably 4.0 or more.

Further, the airbag fabric according to the present invention has a heat history during the production of the yarn, and copper salts and other organic compounds as oxidation inhibitors for the purpose of preventing heat, light and oxidation deterioration during storage and use during production. It is preferable to include an inorganic compound. Normally, copper iodide, copper chloride, copper bromide, copper acetate, copper stearate, and other inorganic and organic acid copper such as copper stearate are added in an amount of 10 to 300 ppm, preferably 20 to 150 ppm as copper, and potassium iodide and bromide are added. Potassium, potassium chloride, sodium iodide, sodium bromide, sodium chloride, lithium iodide,
An alkali metal halide such as lithium bromide and lithium chloride, or an earth metal halide, or a quaternary ammonium halide salt is added in an amount of 0.05 to 0.5% by weight.
Further, if necessary, an organic or inorganic phosphorus compound
Add 500 ppm together.

The above polymer is melt-spun at a spinning temperature of 285 to 315 ° C., and the residence time in the spinning machine after melting the polymer is within 10 minutes, preferably within 1 to 5 minutes. When the spinning temperature is high or the residence time is long, the polymer is thermally decomposed. On the other hand, when the spinning temperature is low or the residence time is short, the unmelted polymer is mixed into the fiber and a stable spinning state is not maintained.

After confirming the normal spinning condition of the molten polymer, the polymer is passed through a spinning pack incorporating a metal nonwoven fabric having pores of about 5 to 30μ and spun through a die. Immediately below the base, it is surrounded by a heating tube having a length of 10 to 100 cm, preferably 20 to 50 cm, and the inside of the heating tube is at least 250 ° C., preferably 300 ° C.
Seal with a high temperature inert gas of ~ 400 ° C to prevent thermal oxidation of spun yarn. Since the spinning temperature and the ambient temperature under the cap are high,
This is because thermal oxidation degradation during the passage of the spun yarn in the heating cylinder cannot be ignored.

The control of the high-temperature atmosphere immediately below the base is particularly necessary to enhance the uniformity between the individual yarns constituting the yarn, whereby a yarn with less fluff can be manufactured, and a high-quality airbag fabric. Is obtained.

The spun yarn is cooled and solidified by cold air after passing through the high-temperature atmosphere, then is applied with an oil agent, and is then taken up by a take-up roll for controlling the spinning speed.

The undrawn yarn taken up by the take-up roll is usually drawn continuously, but may be drawn once and then drawn in another step. In the case of high-speed spinning at a spinning speed of 3000 m / min or more, generally, the film is once wound and then stretched in another step.

The undrawn yarn taken by the take-up roll as described above is 20
Hot stretching is performed at a temperature of 0 ° C. or more, preferably 220 to 260 ° C. The stretching is preferably multi-stage stretching of two or more stages, and the stretching ratio varies depending on the birefringence of the undrawn yarn, and the stretching temperature, the distribution of the stretching during multi-stage stretching, and the like, but 1.5 to 6.0 times.
Preferably it is 2.0-5.5.

By the above method, a polytetramethylene adipamide fiber having a strength of 8.5 g / d or more, an elongation of 15% or more, and a boiling water shrinkage of 5% or less is obtained, and air using the polytetramethylene adipamide fiber is obtained. The base fabric for bags has a tensile strength of 180 kg /
3 cm, tear strength is 18 kg / 2.54 cm and the flexibility measured by the cantilever method becomes 70mm or less, further, since it is also possible to satisfy the burst strength 45 kg / cm ² of the base fabric, has excellent storability, The airbag obtained by weaving the yarn becomes extremely lightweight.

Next, the present invention will be described with reference to Examples. The definitions of the fiber properties and the measuring methods described in the text of the present specification and the Examples are as follows.

(A) Relative viscosity of sulfuric acid 0.25 g of a sample was dissolved in 25 ml of 98% sulfuric acid and measured at 25 ° C. with an Ostwald viscometer.

(B) Strength and elongation of yarn: Based on JIS L1017.

(C) Boiling water shrinkage ratio of yarn Yarn is based on JIS L1073.

(D) Tensile strength of base fabric: Measured with a sample width of 3 cm according to JIS K6328 (strip method).

(E) Tear strength of base fabric: JIS K6328 (Travezoid method), sample width 2.54
Measured in cm.

(F) Burst strength of base fabric: Based on JIS K6328 (Mullen method).

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

(H) Foldability: The bulkiness (cm) when four base cloths of 20 × 20 cm were woven was measured and used as a parameter of the storability.

[Examples] Examples 1 to 5 Spinning speed using tetramethylene adipamide as a main component, hexamethylene adipamide unit as a copolymer component in a small ratio, and polymers having different sulfuric acid relative viscosities. And melt-spun. Using an extruder-type spinning machine, the discharge rate was changed in accordance with the spinning speed and the yarn fineness so that the residence time of the molten polymer in the spinning machine was about 3 minutes.

Prior to spinning, cupric acetate was added as a thermal antioxidant to 0.1 g.
02% by weight, potassium iodide 0.1% by weight, potassium bromide
0.1% by weight was mixed.

The hole diameter of the die is 0.3mmφ, and the number of holes is about 3
It was determined in consideration of the total fineness of the drawn yarn, the spinning speed, the drawing speed, and the like so as to be ~ 6 denier.

The molten polymer was filtered through a stainless steel non-woven fabric having pores of about 15μ in a spin pack.

A heating cylinder having a length of 20 cm was attached directly below the base, and the atmosphere in the cylinder was heated to 280 ° C. A horizontal 120cm long uni-flow chimney is attached under the heating cylinder, and a 20 ° C cold air is blown onto the yarn at a speed of 30m / min.
Cooled and solidified. Then, after applying the oil agent, the yarn speed was controlled by a take-off roll, and then the film was continuously drawn without being wound once. The film was stretched in two steps by a Nelson-type roll, and then heat-treated while giving 3% relaxation, and wound.
The stretching conditions are as follows: the take-up roll is 80 ° C, the first stretch roll is 110
° C and the second stretching roll was at 240 ° C. After the stretching roll, a relaxation heat treatment was performed between the stretching roll and the second stretching roll using a non-heated tension adjusting roll. One-stage stretching ratio is 75% of the total stretching ratio.
%, And stretched while changing the total stretching ratio. The fineness of the drawn yarn was adjusted by changing the discharge amount so as to be about 420 denier.

A part of the obtained yarn was warped by warping, and a part of weft was woven in an air jet loom. The weft driving speed was 800 prm.

The production conditions of the yarn, the characteristics of the raw yarn, and the characteristics of the base fabric for an air bag are shown in the table.

The base fabric for an airbag according to the present invention is different from having the desired mechanical properties, flexibility and storability.

Comparative Examples 1 to 5 Under the same spinning conditions as in Examples 1 to 5, the polymer species specified in the present invention and yarns having different high elongation characteristics were produced, respectively. Fabrics were made. The production conditions, yarn characteristics, airbag fabric characteristics, and the like are shown in the table.

[Effects of the Invention] The airbag obtained by using the airbag base fabric according to the present invention has excellent mechanical properties and heat resistance, and is flexible, has a small storage volume, and is lightweight.
Ideal as a base fabric for non-coated airbags. As a result, by using the airbag base fabric according to the present invention, it is possible to reduce the size and weight of all pairs of devices that house the airbag.

Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI D03D 15/00 D03D 15/00 A (56) References JP-A-64-41438 (JP, A) JP-A-4-176750 (JP, A JP-A-1-104848 (JP, A) JP-A-61-108748 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) D03D 1/02 D03D 15/00

Claims (2)

(57) [Claims] 1. A high-polymerization degree polytetramethylene as a warp and / or a weft of a base fabric for an air bag, wherein 90 mol% or more of polymer constituent units are tetramethylene adipamide units and sulfuric acid relative viscosity is 3.5 or more. Made of adipamide fiber, strength is 8.5g / d or more, elongation is 15% or more, and
A base fabric for an air bag, wherein a polytetramethylene adipamide fiber yarn having a boiling water shrinkage of 5% or less is used. 2. The base fabric for an air bag according to claim 1, wherein the base fabric has the following mechanical properties and flexibility. Tensile strength ≧ 180kg / 3cm Tear strength ≧ 18kg / 2.54cm Flexibility (cantilever method) ≦ 70mm