JP2002173825A - Synthetic fiber for air-bag fabric and air-bag fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synthetic fiber for a noncoated air-bag fabric capable of being stored in a compact state, and having excellent impact resistance and air permeation blocking ability even after long passage of time in a state where it is folded. SOLUTION: The synthetic fiber for a noncoated air-bag fabric has excellent balance as shown below: an initial modulus is 25-60 cN/dtex; a stretch modulus recovery is >=85%; a breaking strength is >=5.0 cN/dtex; a breaking elongation is >=18%; and a dry heat shrinkage percentage at 180 deg.C is >=10%. Further, it is preferable that the main recurring unit of the synthetic fiber is polytrimethylene terephthalate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic fiber for an airbag base fabric for ensuring safety. More specifically, the present invention relates to a synthetic fiber for a non-coated airbag base fabric having no resin coat layer on the surface.

[0002]

2. Description of the Related Art In recent years, the improvement of an inflator for operating an air bag has made it possible to lower the temperature of a high-pressure gas that expands instantaneously, and to make it possible to store air more compactly without resin coating or impregnation. Airtight woven fabrics for backing fabrics (non-coated airbag fabrics) have been put to practical use.

[0003] The characteristics required for such a non-coated airbag are that, even if the thickness of the base fabric is small, the high pressure gas-blocking property is high, and the impact resistance and durability that can withstand instantaneous expansion are provided. Is that when inflated, there is little irritation when it comes into contact with the human body, especially the face.

[0004] To solve these problems, various non-coated airbag base fabrics have been proposed. For example,
JP-A-4-21437 and JP-A-7-48717
In Japanese Patent Application Laid-Open Publication No. H11-264, a non-coated airbag base fabric made of polyethylene terephthalate fiber is proposed. However, when these polyethylene terephthalate fibers are used, the initial modulus of the fibers is about 65 cN / dte.
x or more, the flexibility of the fabric is low, and there is a problem that the stimulus when in contact with the human body, especially the face when expanded, is large.

[0005] When polyamide fibers such as nylon 66 are used, the flexibility of a fabric is superior to that of polyethylene terephthalate fibers, but can withstand long-term use. Had a problem with the dimensional stability of the

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, to be able to be stored compactly, and to have good impact resistance and ventilation prevention even after being folded for a long time. An object of the present invention is to provide a synthetic fiber for a non-coated airbag base fabric.

[0007]

The synthetic fiber for an airbag base fabric of the present invention has the following physical properties (a) to (e) in a synthetic fiber for an airbag base fabric having no resin coating layer on the surface. It is characterized by satisfying at the same time. (A) Initial modulus Y (cN / dtex): 25 ≦ Y ≦ 60 (b) Elongation elastic recovery R (%): R ≧ 85 (c) Breaking strength S (cN / dtex): S ≧ 5.0 ( d) Elongation at break E (%): E ≧ 18 (e) Dry heat shrinkage at 180 ° C. HS (%): HS ≧ 10 Further, the polymer constituting the synthetic fiber contains 85% by mole or more of the repeating unit as polytriethylene. Preferably, it is methylene terephthalate.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The initial modulus Y (unit: cN / dtex) of the synthetic fiber for an airbag base fabric of the present invention is in the range of 25 ≦ Y ≦ 60 in order to satisfy low air permeability and impact resistance. It is necessary. More preferably, the range is 30 ≦ Y ≦ 55. If the temperature is too low, the fiber is easily stretched by the impact of the high-pressure gas, and although the breaking strength is improved, there is a problem that the air permeability becomes too large. On the other hand, if it is too high, stress concentration occurs when receiving the impact of the high-pressure gas, and it is easily torn at the stress concentration point. Further, there is a tendency that irritation when contacting the occupant's face during inflation is large.

In order for the airbag base fabric obtained in the present invention to satisfy excellent impact resistance, the elongation elastic recovery ratio R
Is important to be 85% or more. And 95%
Above, most preferably 100% or more. Usually, the airbag base fabric is stored in a folded state for a long period of time, so that a fold mark is formed, and the fiber properties of the fold that has been bent for a long period of time are deteriorated. When the airbag is actually operated and inflated, stress concentration due to the impact of the high-pressure gas is generated in the fold portion, and the airbag is easily ruptured. The higher the elongation elastic recovery rate of the fibers constituting the base fabric, the smaller the habit of the fold, the less stress concentration occurs during expansion, and the same impact resistance as when mounted can be obtained.

In order to achieve both the mechanical strength characteristics and the flexibility of the fabric, in addition to the requirement of the initial modulus of the fiber, it is necessary that the breaking strength E (tensile strength) is not less than 5.0 cN / dtex. And more preferably 6.0 cN / dtex or more. If the breaking strength is low, it is difficult to satisfy mechanical properties such as impact resistance and burst resistance. Further, when the breaking strength of the fiber is low, it is necessary to increase the basis weight in order to increase the strength of the airbag, and the storage property of the airbag is reduced.

The elongation at break of the fiber must be at least 18.0%, and more preferably at least 20% and at most 35%. If the elongation at break is less than 18%, the resulting fabric is hard and inferior in flexibility, and has poor storage properties. In addition, fluffing and yarn breakage tend to occur during spinning and weaving, which is inappropriate. On the other hand, if the elongation is too high, the elongation of the fabric itself becomes large, and the amount of gas permeation at the time of inflation increases, so that the fabric cannot be used as a base fabric for an airbag.

[0012] The synthetic fiber of the present invention has the following properties in addition to the above properties.
It is necessary that the dry heat shrinkage at 80 ° C. is 10% or more. Preferably it is 10% or more and 30% or less. If it is less than 10%, it will be difficult to obtain a low-permeability, high-density woven fabric required for a non-coated airbag base fabric even if a shrinkage heat treatment is performed after sewing.

Further, preferred physical properties of the synthetic fiber for an airbag base fabric of the present invention will be described. Single fiber fineness is 3.0 dtex
The following is preferred. More preferably, 1.0 to 2.2 dt.
ex. If it exceeds 3.0 dtex, the air permeability required for the non-coated airbag fabric (0.20 c
c / cm ² /sec/0.5 inch Aq. Or less, preferably 0.15 cc / cm ² /sec/0.5 inch
Aq. ) Tends to be difficult to achieve. Also, the bulk when molded into an airbag tends to be large, and the storage property tends to be reduced. On the other hand, if it is less than 1.0 dtex, single yarn breakage during spinning tends to occur, making it difficult to spin and tend to cause fluff.

The synthetic fiber for an air bag of the present invention can be used without any particular limitation as long as it satisfies the above characteristics.
Considering ease of production, etc., polytrimethylene terephthalate fibers made of polyester in which 85 mol% or more of the repeating units of the polymer constituting the synthetic fibers are polytrimethylene terephthalate are most preferred. The third component may be copolymerized with the polymer in a range that does not impair the object of the present invention, for example, 15 mol% or less, preferably 5 mol% or less based on all acid components. Examples of preferably used copolymerization components include conventionally known acid components and glycol components. Among them, the copolymerization of a bifunctional phosphorus compound has the effect of reducing the flame retardancy of the obtained airbag. It is preferable because it improves. In this case, the amount of copolymerization is suitably in the range of 0.3 to 1.5% by weight, preferably 0.6 to 1.1% by weight, as the amount of phosphorus element.
If the phosphorus element is less than 0.3% by weight, the flame retardancy tends to decrease, while if it exceeds 1.5% by weight, the fiber strength tends to decrease. Preferably used 2
As the functional phosphorus compound, for example, a phosphonic acid derivative or a phosphinic acid derivative represented by the following [Formula 1] or [Formula 2] can be exemplified.

[0015]

Embedded image

[0016]

Embedded image

In the formula, R ₁ represents a hydrocarbon group having 1 to 18 carbon atoms, R ₂ and R ₃ are the same or different groups and represent a hydrogen atom or a hydrocarbon group, and R ₄ is a divalent group. X represents a carboxy group or an ester thereof. Specifically, dimethyl phenylphosphonate, (2-
(Carboxylethyl) methylphosphinic acid and the like are preferably used.

When the synthetic fiber is a polyester fiber, the intrinsic viscosity of the polyester fiber used is 0.7.
It is preferably at least 0.8, and more preferably at least 0.8. When the intrinsic viscosity is less than 0.7, the breaking strength and impact resistance tend to decrease. In addition, the intrinsic viscosity of the polyester fiber is preferably 1.5 or less, and more preferably 1.3 or less, from the viewpoint of the spinning property and the like.

The above-described synthetic fiber for an airbag base fabric according to the present invention can be produced by the following method, for example, by describing a polymethylene terephthalate fiber.

That is, a polytrimethylene terephthalate polymer having an intrinsic viscosity of 0.8 or more is melted and discharged, and the discharged yarn is allowed to pass through an atmosphere heated to a temperature higher than the melting point, and then cooled by cooling air. Allow to solidify, oil solution to 0.
And a spinning speed of 500 to 1000%.
Withdraw at a speed of m / min. The obtained undrawn yarn is preheated at a temperature equal to or higher than the glass transition point, drawn 4.0 to 6.0 times at a draw ratio corresponding to the take-up speed of the undrawn yarn, and then drawn at 120 ° C.
It is obtained by heat setting and winding at a temperature of ２００200 ° C.

In the present invention, it is more preferable to set the above spinning speed to 1000 m / min or less, since both the breaking strength and the breaking elongation of the present invention by high-magnification stretching and the elastic recovery can be compatible.

By using the synthetic fiber thus obtained, another airbag fabric according to the present invention can be obtained. The synthetic fibers used at this time are multifilaments, and the total fineness after drawing is 220 to 940d.
The range of tex is appropriate. The obtained drawn yarn is subjected to warping in a non-twisted or twisted state, and is woven so that the value of weaving density (books / inch) × √ (filament fineness) is in the range of 920 to 1025, 130-200 after heat setting
Calendering is performed using a roller heated to ° C., and the fabric is further finished into a high-density fabric, which is used as a base fabric for an airbag. At this time, it is preferable that tension is applied by a pin tenter or the like so that wrinkles or the like do not occur in the woven fabric.

[0023]

The present invention will now be described in more detail with reference to Examples and Comparative Examples, which by no means limit the present invention.
The physical properties and measured values in the examples were determined as follows.

(1) Intrinsic viscosity IV The viscosity was measured at 30 ° C. by a standard method using a phenol / tetrachloroethane = 1/1 mixed solvent.

(2) Fineness D The fineness was measured according to JIS-L1013.

(3) Breaking strength S, breaking elongation E, and initial modulus Y According to the method of JIS-L1013, the breaking strength, breaking elongation,
The initial modulus was measured.

(4) Dry heat shrinkage at 180 ° C. Load of 0.88 mN / dtex (0.10 g / de) was applied to measure the length (L ₀ ) of the raw yarn, and then no load was applied during dry heat at 180 ° C. was introduced into the yarn length L ₁ after 30 minutes was measured by a load 0.88mN / dtex (0.10g / de) , it was calculated from the following equation. HS (%) = (L ₀ −L ₁ ) / L ₀ × 100

(5) Elongation Elasticity Recovery Rate Elongation elasticity recovery rate was measured according to the method defined in JIS-L1013. After leaving the fiber for 24 hours in a room where the temperature and humidity are controlled at 20 ° C. and 65% RH, the fiber is stretched 10% at a yarn length of 20 cm and a pulling speed of 2 cm / min by a tensile tester.
Immediately after removing the weight and returning to the original gripping interval, 2c
It was pulled at a pulling speed of m / min. And the elastic recovery rate was calculated | required by the following formula. Elastic recovery rate (%) = (L−L ₁ ) / L × 100 L: Elongation at 10% elongation (mm, here 20 mm) L ₁ : Residual strain (mm) after the first tension

(6) Flame retardancy (coil method) This is a value measured according to JIS-L-1091 (D).

(7) Air permeability (after folding) Using an airbag base fabric, a 60 L capacity (700 m diameter)
m) Create an airbag and apply it from the left and right
After folding into a bellows four times, folding it up and down four times each from the top and bottom to a size of 150 mm x 150 mm, applying a 4 kg load to the folded airbag
Left for days. Thereafter, the air permeability was measured according to JIS-L-1096.
This is a value measured by the Frazier method.

(8) Burst pressure (after folding) A 60 L capacity (700 m diameter)
m) Create an airbag and apply it from the left and right
After folding into a bellows four times, folding it up and down four times each from the top and bottom to a size of 150 mm x 150 mm, applying a 4 kg load to the folded airbag
Left for days. After that, a folded air bag was installed on a high-speed burst tester of Ito Seiki Co., Ltd.
Nitrogen gas compressed to cm 2 G is instantaneously introduced and burst at 20 to 40 msec, and the pressure value at that time is defined as a burst pressure.

(9) Scratching property A metal plate which is sufficiently contacted when the airbag is activated,
When a 10 mm-thick vulcanized rubber (hardness 70: value measured by YARN HARDNESS manufactured by Yokogawa Wezac Co., Ltd.) is fixed, and when the airbag is activated, scratches (5 mm or more) formed on the vulcanized rubber surface are visually observed. It was evaluated by judgment. ：: 4 scratches or less △: 5 to 19 scratches ×: 20 or more scratches

Example 1 A polytrimethylene terephthalate (PTT) chip having an intrinsic viscosity of 0.65 was pressed under reduced pressure to 1
Solid phase polymerization was performed at 80 ° C. to obtain chips having an intrinsic viscosity of 0.85. The chips are melted and discharged at 275 ° C. according to the intrinsic viscosity, and solidified by cooling with cooling air at 25 ° C.
Wound at a speed of minutes. After the obtained undrawn yarn was preheated with a heating roller at 70 ° C., it was drawn at a draw ratio of 5.5 times,
Heat set at 80 ° C to 470dtex / 192fi
1 polyester fiber was obtained. The obtained polyester fiber was twisted at 150 T / m, woven into a plain weave, subjected to scouring and heat setting. Next, using a metal roll calender, the linear pressure was 200 kg / cm, the speed was 6 m / min, and the temperature was 1
Thermal processing was performed at 50 ° C. The obtained airbag base fabric has a woven density of 55 threads / inch, a weft of 50 threads / inch, and a thickness of 0.
It was a 22 mm woven fabric. Table 1 shows the fiber properties of the obtained examples and the properties of the base fabric.

[Examples 2 to 4 and Comparative Examples 1 to 5] Except that the intrinsic viscosity, the melting temperature, the spinning speed, the stretching ratio, the stretching temperature and the heat setting temperature of the chips after the solid phase polymerization were changed as shown in Table 1. In the same manner as in Example 1, a polyester fiber was produced to obtain an airbag base fabric. Table 1 shows the physical properties of the fibers and the base fabric of the obtained examples and comparative examples.

[Comparative Example 6] A polyethylene terephthalate (PET) chip having an intrinsic viscosity of 0.65 was placed under reduced pressure at 230
Solid-state polymerization was carried out at ℃ to obtain chips having an intrinsic viscosity of 0.98. The chips were melted and discharged at 300 ° C. according to the intrinsic viscosity, cooled and solidified by cooling air at 25 ° C., and wound up at a speed of 700 m / min. After preheating the obtained undrawn yarn with a heating roller at 90 ° C., it was drawn at a draw ratio of 5.2 times,
470dtex / 192fil by heat setting at 0 ° C
Was obtained. An airbag fabric was obtained in the same manner as in Example 1, except that the polyester fiber thus obtained was used. The evaluation results are shown in Table 1.

[0036]

[Table 1]

[0037]

The synthetic fibers constituting the airbag base fabric of the present invention have a good balance of initial modulus, breaking strength, breaking elongation and elongation elastic recovery.
Using this as an airbag base fabric, the impact resistance, especially the burst resistance due to stress concentration due to the fold after storage is improved,
It has good ventilation prevention properties, can be stored compactly, and can highly satisfy the performance required of a non-coated airbag base fabric that reduces the impact on the occupant's face when inflated.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) D03D 1/02 D03D 1/02 15/00 15/00 A F term (Reference) 3D054 CC26 CC47 FF02 FF03 FF11 FF13 FF18 FF20 4L035 BB31 BB56 BB89 BB91 CC01 EE02 EE08 EE09 EE14 EE20 FF01 FF10 GG05 HH10 4L048 AA22 AA48 AA49 AA50 AA51 AA53 AB07 AC09 AC10 AC11 AC12 AC14 BA01 CA01 CA02 CA03 CA06 CA25

Claims (4)

[Claims] 1. A synthetic fiber for an airbag base fabric, which does not have a resin coat layer on its surface, characterized by satisfying the following physical properties (a) to (e) simultaneously. (A) Initial modulus Y (cN / dtex): 25 ≦ Y ≦ 60 (b) Elongation elastic recovery R (%): R ≧ 85 (c) Breaking strength S (cN / dtex): S ≧ 5.0 ( d) Elongation at break E (%): E ≧ 18 (e) Shrinkage rate at 180 ° C. dry heat HS (%): HS ≧ 10 2. The synthetic fiber for an airbag base fabric according to claim 1, wherein the polymer constituting the synthetic fiber is polytrimethylene terephthalate in which at least 85 mol% of the repeating units are polytrimethylene terephthalate. 3. The synthetic fiber for an airbag base fabric according to claim 1, wherein the polymer constituting the synthetic fiber contains 0.3 to 1.5% by weight of a bifunctional phosphorus compound as a phosphorus element. 4. An airbag base fabric woven using the synthetic fiber for an airbag base fabric according to claim 1.