JPH0835116A - Polyester fiber for air bag base fabric - Google Patents

Abstract

PURPOSE:To obtain polyester fibers reduced in single fiber fineness, increased in both mechanical strength and elongation, and reduced in the compressive stress in the single fiber sectional direction, thus capable of giving air bag base fabrics good in air impermeability and storability and excellent in impact resistance and durability. CONSTITUTION:The objective polyester fiber has the following characteristics: intrinsic viscosity: 20.8 (owing to solid phase polymerization); ethylene terephthalate unit accounts for 2 90mol% of the total recurring units; single fiber fineness: 0.3-4.0 denier; tenacity: >=8.0g/de; tensile elongation: >=14%; and sectional compressive stress: <=20kg/mm<2>. Using the polyester fibers, highly airtight and high-density woven fabrics can be easily obtained, with adequate impact resistance even in the case of low base fabric basis weight.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyester fiber suitable for an airbag for ensuring safety. More specifically, impact resistance even without coating,
The present invention relates to a polyester fiber capable of obtaining a shock absorbing airbag having excellent durability.

[0002]

2. Description of the Related Art In recent years, airbag systems have been put into practical use in order to ensure passenger safety in the event of an automobile collision. The airbag is usually folded and stored, and when a collision is detected, the airbag is inflated by high-pressure gas and installed so as to ensure the safety of an occupant. Therefore, important properties required for the airbag base fabric are high air-permeability of high-pressure gas, impact resistance capable of withstanding momentary inflation, and durability capable of long-term storage. Can be mentioned.

However, since nylon fibers which have been widely used in the past have good impact resistance, they have high hygroscopicity.
There is a problem in terms of durability such that the yarn absorbs moisture after storage for a long period of time, the diameter of the single yarn becomes large, and in the case of a non-coated airbag base fabric which is not coated, the air permeability is lowered.

On the other hand, in Japanese Patent Application Laid-Open Nos. 3-167312 and 3-167046, the toughness is 12
Polyester fibers for airbags having a knot strength of 0 or more and a knot strength of 4.1 g / d or more and improved impact resistance have been proposed, but all of these fibers have compressive stress (about 22 kg / mm) in the fiber cross-sectional direction. ^{Since 2} ) is large, energy absorption due to deformation in the fiber cross section is small. Therefore, in the case of the non-coated airbag base fabric, there is a problem that the base fabric weight becomes large and the storability is deteriorated when it is attempted to satisfy both the airflow blocking property and the impact resistance.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned drawbacks of the polyester fiber for air bag base fabric, to provide good impact resistance and air flow blocking property, and to have excellent durability and storability. An object of the present invention is to provide a polyester fiber from which an airbag base fabric can be obtained.

[0006]

The above object is a polyester fiber for an airbag base fabric, wherein 90 mol% or more of repeating units are ethylene terephthalate, and the fiber has the following requirements (a) to (e). At the same time, it is achieved by a polyester fiber for an airbag base fabric, which is characterized by satisfying at the same time. (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% Above (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, 90% or more of the repeating units of the polyester must be ethylene terephthalate, and preferably 95% or more. is there. The copolymerizable component may be any conventionally known acid component or glycol component,
Among them, copolymerization of bifunctional phosphorus compounds,
It is preferable because the flame retardancy of the obtained airbag is improved.
In this case, as a copolymerization amount, a phosphorus element amount of 0.3 to
A suitable range is 1.5% by weight, preferably 0.6-1.
It is 1% by weight. If the amount of elemental phosphorus is less than 0.3% by weight, the flame retardancy becomes insufficient, while if it exceeds 1.5% by weight, the strength of the fiber decreases.

Examples of preferably used bifunctional phosphorus compounds include phosphonic acid derivatives or phosphinic acid derivatives represented by the following formula (I) or (II).

[0008]

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. Represents an organic group, and X represents a carboxyl group or an ester thereof. Specifically, dimethyl phenylphosphonate,
(2-Carboxylethyl) 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 airbag is instantaneously It is possible to improve the shock absorbing property when expanded. When the intrinsic viscosity is less than 0.80, the strength and the toughness represented by √ (elongation) cannot be increased, and the impact resistance becomes insufficient. If the intrinsic viscosity is too high, the spinnability tends to decrease, so
It is preferably 1.0 or less.

It is important that the monofilament fineness D is in the range of 0.5 to 4.0 denier, preferably 1.0 to 2.0 denier from the viewpoint of air bag storability (flexibility) and air permeability. Is. When it exceeds 4.0 denier, it is not preferable because not only the flexibility of the base fabric is lowered and the storability is lowered, but also the air blocking property is lowered. On the other hand, when it is less than 0.5 denier, when weaving into a high-density fabric for use as an air bag base fabric, fluff is likely to occur and stable weaving becomes impossible.

Further, the tensile strength T must be 8.0 g / de or more and the tensile elongation E must be 14% or more. When the tensile strength is less than 8.0 g / d, it is essential to increase the basis weight of the base cloth in order to increase the strength of the airbag, and the storability of the airbag is deteriorated. On the other hand, even if the tensile strength is sufficiently high, if the tensile elongation is less than 14%, it becomes difficult to absorb high energy at the time of impact, resulting in insufficient fiber for airbag. In addition,
If the tensile strength is too high, the tensile elongation tends to be insufficient. Conversely, if the tensile elongation is too high, the tensile strength tends to be insufficient. Therefore, the tensile strength is 10 g / d or less and 20%, respectively.
It is desirable to make the following.

In addition to the above characteristics, the polyester fiber of the present invention has a compressive stress F of 20 in cross section in order 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
Is essential. By doing so, deformation is generated in the cross-sectional direction of the fibers at the woven intersection points of the fibers forming the base fabric, and the impact energy is absorbed, so that the impact resistance can be improved.

The cross-section compressive stress F referred to here is 40 of the single fiber diameter, which is obtained by compressing in the cross-sectional direction of the single fiber with a plane indenter (diameter of 50 μm) using a micro compression tester (MCTM-500 manufactured by Shimadzu). The load generated at the time of% compression is measured, and F =
It is calculated by (generated load / contact area with plane indenter).

The polyester fiber of the present invention described above can be obtained, for example, by the following method. That is, a polyester whose intrinsic viscosity is increased by solid-state polymerization or the like, usually 0.8
Melt and discharge 5 or more polymers at about 300 ℃
After passing through the above heating zone, it is cooled and solidified, and after applying an oil agent, it is wound at a take-up speed of 500 to 1000 m / min. Next, in order to reduce the compressive stress F in the cross-sectional direction, the obtained undrawn yarn is first contacted with a heating roller having a temperature of 50 ° C. to a glass transition point for at least 1 second and preheated, and then the glass transition point or more and 150 ° C. or less. First stage drawing at a draw ratio of 2.5 to 4.0 while passing in a heating atmosphere in a non-contact manner for at least 1 second, and then full stretching while passing in a heating atmosphere at 200 to 230 ° C in a non-contact manner for at least 1 second. The second stage drawing is performed so that the magnification is 4.0 to 6.0, and the film is passed through a heating atmosphere at 200 to 230 ° C. for at least 1 second in a non-contact manner without contacting with a heating roller, and then 5
Obtained by heat treatment of relaxation contraction of -15%. In other words, it is important to suppress the crystallization of the fiber surface by using a non-contact type heat source for heat stretching and relaxation heat treatment. It is presumed that the crystallization of the part proceeds, and it is not possible to obtain fibers with a low cross-section 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 in a non-twisted or twisted state and woven, but in the case of weaving in a non-twisted state, in order to further improve the weavability and the airtightness of the obtained base fabric, It is preferable that 20 to 50 fibers / m of entanglement be imparted to the fibers.

The weaving method is not particularly limited, but for air bag base cloth, weaving is usually performed so that the value of weave density (books / inch) × √ (thread fineness) is in the range of 920 to 1025,
After scouring and heat setting, calendering is carried out using a roller heated to 130 to 200 ° C. to further fabricate a high density fabric. At that time, it is preferable to apply tension by a pin tenter or the like so that the fabric is not wrinkled.

[0018]

Since the polyester fiber of the present invention has a small single fiber fineness, a high density woven fabric having a high airtightness can be easily obtained. Further, in addition to high strength and elongation, the compressive stress in the cross section direction of the single fiber is small, so that it is possible to absorb impact energy even when the fiber is deformed in the cross section direction. Impact resistance can be achieved and storability is improved.

[0019]

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

Example 1 Polyethylene terephthalate chips having an intrinsic viscosity of 1.00 were melted at a temperature of 300 ° C., and then discharged at a discharge rate of 200 g / minute from a spinneret having 249 discharge holes having a diameter of 0.35 mm. , Length 200
mm After passing through a zone heated and held at a temperature of 350 ° C., cooling air having a temperature of 25 ° C. and an air speed of 0.3 m / sec is sprayed over a blowing length of 330 mm to cool and solidify, and an oiling agent is applied by an oiling roller. It was taken up at a speed of 900 m / min and wound once.

2. 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.
Stretched 3 times in the first stage, then stretched 1.6 times while heating in a dry heat bath at 220 ° C for 1 second, and then further stretched at 220 ° C.
7% relaxation treatment in the dry heat bath, followed by a pressure of 2.5k
It was entangled with compressed air of g / cm ² and wound at a speed of 300 m / min.

Then, the obtained multifilament was woven with a water jet loom into a plain weave having a weaving density of 53 warps / inch and weft 53 threads / inch, and then subjected to scouring and heat setting. Next, 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. The results are shown in Table 1.

[Examples 2 to 4, Comparative Examples 1 to 7] The same procedure as in Example 1 was 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. In Comparative Example 2, a spinneret having 96 discharge holes was used, and in Comparative Examples 6 and 7, heating was performed using a heating roller. Stretching was performed. The results are summarized in Table 1.

[0024]

[Table 1]

Claims (1)

[Claims] 1. A polyester fiber for an airbag base fabric, wherein 90 mol% or more of the repeating unit is ethylene terephthalate, and the fiber simultaneously satisfies the following requirements (a) to (e). 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% Above (e) Cross-sectional compressive stress F is 20 kg / mm ² or less