JP2944891B2 - Polyester fiber for airbag base fabric - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester fiber suitable for an airbag for ensuring safety. In more detail, impact resistance even without coating,
The present invention relates to a polyester fiber from which a shock-absorbing airbag having excellent durability can be obtained.

[0002]

2. Description of the Related Art In recent years, airbag systems have been put into practical use for ensuring the safety of occupants in the event of an automobile collision. Usually, the airbag is folded and stored, and is inflated by high-pressure gas when a collision is detected, and is installed so as to ensure the safety of the occupant. Therefore, the important characteristics required for the airbag base fabric include high airflow resistance to high-pressure gas, impact resistance to withstand instantaneous inflation, and durability for long-term storage. There are things.

[0003] However, conventionally used nylon fibers have good impact resistance but large hygroscopicity.
When stored for a long period of time, it absorbs moisture to increase the diameter of a single yarn, and in the case of a non-coated airbag base fabric which is not coated, there is a problem in durability such as a decrease in air permeability.

On the other hand, JP-A-3-167312 and JP-A-3-167046 disclose a toughness of 12%.
Polyester fibers for airbags having an impact resistance of 0 or more and a knot strength of 4.1 g / d or more have been proposed. All of these fibers have a compressive stress (about 22 kg / mm) in the fiber cross-sectional direction. ² ) Large energy absorption due to deformation in the cross-section of the fiber is small. For this reason, in the case of using a non-coated airbag base fabric, there is a problem that the base fabric weight is increased and the storage property is reduced if it is attempted to simultaneously satisfy the ventilation prevention property and the impact resistance.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the above-mentioned polyester fibers for an airbag base fabric, to have good impact resistance and good ventilation prevention properties, and to have excellent durability and storage properties. An object of the present invention is to provide a polyester fiber from which an airbag base fabric can be obtained.

[0006]

The object of the present invention is to provide a polyester fiber for an airbag base fabric, wherein at least 90 mol% of the repeating unit is ethylene terephthalate, wherein the fiber satisfies the following requirements (a) to (e). This is achieved by the polyester fiber for the airbag base fabric, which is simultaneously satisfied. (A) Intrinsic viscosity IV is 0.8 or more (b) Single fiber fineness D is 0.3 to 4.0 denier (c) Tensile strength T is 8.0 g / de or more (d) Tensile elongation E is 14% (E) The cross-sectional compressive stress F is 20 kg / mm ² or less In the polymer constituting the polyester fiber of the present invention, it is necessary that 90% or more of the repeating unit of the polyester is ethylene terephthalate, and preferably 95% or more. is there. Examples of the copolymerizable component include conventionally known acid components and glycol components.
Among them, copolymerization of bifunctional phosphorus compound,
It is preferable because the flame retardancy of the obtained airbag is improved.
In this case, the copolymerization amount is 0.3 to
A range of 1.5% by weight is suitable, preferably 0.6-1.
1% by weight. If the phosphorus element content is less than 0.3% by weight, the flame retardancy becomes insufficient, while if it exceeds 1.5% by weight, the fiber strength decreases.

As the bifunctional phosphorus compound preferably used, for example, a phosphonic acid derivative or a phosphinic acid derivative represented by the following formula (I) or (II) can be exemplified.

[0008]

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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 and each represents a hydrogen atom or a hydrocarbon group, and R ₄ represents a divalent group. X represents a carboxyl group or an ester thereof. Specifically, dimethyl phenylphosphonate,
(2-Carboxyethyl) methylphosphinic acid and the like are preferably used.

Next, by setting the intrinsic viscosity of the polyester fiber of the present invention to 0.80 or more, preferably 0.8 to 1.0, the strength and durability of the airbag are improved, and the instant It is possible to improve the shock absorbing property when expanded. When the intrinsic viscosity is less than 0.80, strength and toughness represented by √ (elongation) cannot be increased, and impact resistance becomes insufficient. In addition, since the spinnability tends to decrease if the intrinsic viscosity is too high,
It is preferably 1.0 or less.

It is important that the single fiber fineness D is in the range of 0.3 to 4.0 deniers, preferably 1.0 to 2.0 deniers, from the viewpoint of the storage property (flexibility) and air permeability of the airbag. It is. If it exceeds 4.0 denier, not only is the flexibility of the base fabric reduced, so that not only the storability but also the air permeability is reduced, which is not preferable. On the other hand, when it is less than 0.3 denier, when weaving into a high-density woven fabric for an airbag base fabric, fluff is liable to occur, and stable weaving cannot be performed.

Further, it is necessary that the tensile strength T is 8.0 g / de or more and the tensile elongation E is 14% or more. If the tensile strength is less than 8.0 g / d, it is necessary to increase the basis weight of the base fabric in order to increase the strength of the airbag, and the storage property of the airbag decreases. On the other hand, if the tensile elongation is less than 14% even if the tensile strength is sufficiently high, it becomes difficult to absorb high energy at the time of impact, and the fiber for an airbag becomes insufficient. In addition,
If the tensile strength is too large, the tensile elongation tends to be insufficient, and if the tensile elongation is too large, the tensile strength tends to be insufficient.
It is desirable to make the following.

[0013] In addition to the above-mentioned characteristics, the polyester fiber of the present invention has a cross-sectional compressive stress F of 20 to reduce the impact force in the tensile direction applied to the base fabric when the airbag is operated.
kg / mm ² or less, preferably 20 to 15 kg / mm ²
It is important that By doing so, at the weaving intersection of the fibers constituting the base fabric, deformation in the fiber cross-sectional direction occurs and the impact energy is absorbed, so that the impact resistance can be improved.

The section compressive stress F as used herein refers to a value obtained by compressing in the cross section direction of a single fiber with a plane indenter (50 μm diameter) using a microcompression tester (MCTM-500, manufactured by Shimadzu) and %, The stress generated when compressed is measured.
It is calculated by ( stress generated at 40% compression / contact area between plane indenter and fiber ).

The polyester fiber of the present invention described above is obtained, for example, by the following method. That is, a polyester whose intrinsic viscosity is increased by solid phase polymerization or the like, usually 0.8
5 or more polymers are melted and discharged at about 300 ° C.
After passing through the above heating zone, it is cooled and solidified, and after applying the oil agent, it is wound at a take-up speed of 500 to 1000 m / min. Next, the obtained undrawn yarn is first brought into contact with a heating roller having a temperature of 50 ° C. to a glass transition temperature for at least 1 second in order to reduce the compressive stress F in a cross-sectional direction, and after preheating, the glass transition temperature is not less than 150 ° C. First-stage stretching at a stretching ratio of 2.5 to 4.0 while passing through a heating atmosphere without contact for at least 1 second, and then total stretching while passing through a heating atmosphere at 200 to 230 ° C without contact for at least 1 second. The film is stretched in the second stage so that the magnification becomes 4.0 to 6.0, and further passed through a heating atmosphere at 200 to 230 ° C. for at least 1 second without contact without contact with a heating roller.
~ 15% relaxation shrinkage heat treatment. In other words, it is important to suppress the crystallization of the fiber surface by using a non-contact type heat source for the heat drawing and relaxation heat treatment. It is presumed that the crystallization of the portion proceeds, and it is impossible to obtain a fiber having a low sectional compressive stress.

The total fineness of the drawn yarn is suitably in the range of 210 to 840 denier. The obtained drawn yarn is warped and woven in a non-twisted or twisted state, but when woven in a non-twisted state, in order to further improve the weaving property and the airtightness of the obtained base cloth, It is preferable that the fibers are entangled at about 20 to 50 fibers / m.

The weaving method is not particularly limited. For an airbag base fabric, weaving is usually performed so that the value of weaving density (book / inch) × √ (filament fineness) is in the range of 920 to 1025,
After scouring and heat setting, calendering is performed using a roller heated to 130 to 200 ° C., and the fabric is further finished to a high density. 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.

[0018]

The polyester fiber of the present invention has a small single fiber fineness, so that a high-density woven fabric with high airtightness can be easily obtained. In addition to the high strength and elongation, the compressive stress in the cross section direction of the single fiber is small, so that the impact energy can be absorbed by the fiber deformation in the cross section direction. Impact resistance can be achieved, and storage properties are improved.

[0019]

The present invention will be described in more detail with reference to the following examples. In addition, each measurement item followed the following. Intrinsic viscosity (IV) It was determined from the solution viscosity measured at 35 ° C. using orthochlorophenol as a solvent. Tensile strength and elongation (TE) Using a tensile load measuring device (manufactured by Shimadzu, Autograph), JI
It was measured according to SL-1074-64. Sectional compression stress F Using a micro compression tester (manufactured by Shimadzu, MCTM-500)
The single fiber was compressed in the cross-sectional direction with a plane indenter (50 μm diameter), and the stress generated when the single fiber was compressed by 40% of the single fiber diameter was measured, and F was calculated from the following equation. F = generated stress at 40% compression / contact area between flat indenter and fiber Tensile strength and elongation of base fabric Measured by the strip method of JIS L-1096. Air permeability Measured by the Frazier method according to JIS L-1096. Inflation internal pressure A type 4 inflation manufactured by Morton International was attached to a module containing a 60-liter airbag for a driver's seat, and this was heated at 95 ° C. for 6 hours to immediately perform inflation. The internal pressure at this time was measured with a strain gauge (manufactured by Kyowa Dengyo Co., Ltd.). If the inflation internal pressure is 0.3 kg / cm ² or more, the impact resistance is good.

Example 1 A polyethylene terephthalate chip having an intrinsic viscosity of 1.00 was melted at a temperature of 300 ° C., and then discharged at a discharge rate of 200 g / min from a spinneret having 249 discharge holes having a hole diameter of 0.35 mm. , Length 200
After passing through a zone heated and maintained at a temperature of 350 ° C. mm, cooling air at a temperature of 25 ° C. and a wind speed of 0.3 m / sec is sprayed over a blowing length of 330 mm to cool and solidify, and an oil agent is applied by an oiling roller. At a speed of 900 m / min.

The obtained undrawn yarn is preheated with a heating roller at 60 ° C. for 1 second and then heated in a dry heat bath at 150 ° C.
The film is stretched three times in the first step, and then stretched 1.6 times while heating for 1 second in a 220 ° C. dry heat bath.
7% relaxation treatment in a dry heat bath at a pressure of 2.5k
It was entangled with a compressed air of g / cm ² and wound at a speed of 300 m / min.

Next, the obtained multifilament was woven into a plain weave having a weaving density of 53 yarns / inch and a weft of 53 yarns / inch using a water jet loom, and then subjected to scouring and heat setting. Next, when the temperature of the metal roll is 180
Using a pair of metal roll / elastic roll calender at ℃
Thermal processing was performed at a linear pressure of 200 kg / cm and a speed of 6 m / min. Table 1 shows the results.

Examples 2 to 4 and Comparative Examples 1 to 7 The same procedures as in Example 1 were carried out except that the intrinsic viscosity of polyethylene terephthalate and the stretching conditions were changed as shown in Table 1.
The discharge amount was changed so that the single fiber fineness of the obtained drawn yarn was as shown in Table 1, Comparative Example 2 used a spinneret having 96 discharge holes, and Comparative Examples 6 and 7 used a heating roller. Stretching was performed. The results are summarized in Table 1.

[0024]

[Table 1]

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) D01F 6/62 301-308 B60R 21/16 D03D 1/02

Claims (1)

(57) [Claims] 1. A polyester fiber for an airbag base fabric, wherein 90% by mole or more of a repeating unit is ethylene terephthalate, wherein the fiber satisfies the following requirements (a) to (e) at the same time. Polyester fiber for airbag base fabric. (A) Intrinsic viscosity IV is 0.8 or more (b) Single fiber fineness D is 0.3 to 4.0 denier (c) Tensile strength T is 8.0 g / de or more (d) Tensile elongation E is 14% (E) Cross-sectional compressive stress F is 20 kg / mm ² or less