JPH08134721A - Filament yarn for air bag - Google Patents

Abstract

PURPOSE: To obtain polyester filament yarn having mechanical properties such as tensile strength and elongation necessary for air bag base fabric when woven or knitted and capable of giving fabrics with flexibility as well as such mechanical properties. CONSTITUTION: This filament yarn comprises conjugate fibers each of which is made up of core component consisting of polyethylene terephthalate >=0.8 in intrinsic viscosity and sheath component consisting of a copolymer of polyethylene terephthalate and polybutylene terephthalate at the molar ratio of (85:15) to (90:10) with the core/sheath weight ratio of (50:50) to (70:30), having the following characteristics: single fiber fineness: 1-3 denier; total fineness: 200-500 denier; tenacity: >=8g/d: elongation at beak: >=15%; and flexural rigidity satisfy the relationship: B<=5.5×10<-6> ×TD (B is flexural rigidity, g.cm<2> /FY; TD is total fineness, denier).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a yarn for an airbag capable of obtaining an airbag base fabric having excellent mechanical properties and flexibility.

[0002]

2. Description of the Related Art At present, air bags used as a safety device for automobiles are mainly made of a base fabric obtained by coating a synthetic fiber woven fabric using nylon 66 with rubbers.

[0003] Airbags, together with shock absorption, usually
It also needs to be flexible so that it can be stored in a very small space.

However, the base fabric obtained by coating the synthetic fiber woven fabric with rubber can improve heat resistance and airtightness by coating with rubber, but the base fabric becomes hard, so that the storage property is poor. There's a problem.

In order to solve this problem and reduce the manufacturing cost, recently, a non-coated type airbag not covered with rubber has been developed, and the material is nylon 6
It is considered to use polyester which is cheaper than No. 6 and has good heat resistance.

However, polyester is nylon 6
Since it has a higher elastic modulus than that of 6, when it is woven into a base fabric, it has a drawback that it lacks in flexibility. Especially, when it is woven at a high density to improve airtightness, it is more difficult to store it compactly. The problem arises that

Japanese Patent Laid-Open No. 3-167312 proposes a fiber having improved toughness and knot strength as a polyester fiber for an air bag, and an air bag base fabric obtained from this fiber has impact resistance and durability. The flatness of the base fabric is improved.

However, the base fabric obtained from this fiber has a drawback that it is not sufficiently flexible, and if it is woven at a high density in order to increase the airtightness, the storage property becomes poor.

As described above, it is not easy to impart flexibility to the polyester yarn while maintaining strength and durability, and it is possible to obtain a flexible airbag base fabric while being excellent in strength and durability. Polyester yarn has not been developed yet.

[0010]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and is capable of obtaining a base cloth having the mechanical properties and flexibility required for an air bag base cloth at the same time. Providing articles is a technical issue.

[0011]

The present inventors have arrived at the present invention as a result of extensive studies to solve the above problems.

That is, according to the present invention, the core component has an intrinsic viscosity
It is composed of polyethylene terephthalate of 0.8 or more, the sheath component is a copolymer of polyethylene terephthalate and polybutylene terephthalate in a molar ratio of 85/15 to 90/10, and the core / sheath ratio is 50/50 to a weight ratio. A yarn consisting of 70/30 core-sheath structure fibers with a single yarn fineness of 1 to 3
d, total fineness of 200 to 500 d, tensile strength of 8 g / d or more,
A yarn for an airbag, which has a breaking elongation of 15% or more and a bending rigidity within the range of the formula (1).

(1) B ≦ 5.5 × 10 ⁻⁶ × TD B: Flexural rigidity (g · cm ² / thread) TD: Total fineness (d) The present invention will be described in detail below.

The yarn for an air bag of the present invention comprises a composite fiber having a core-sheath structure. The core component is polyethylene terephthalate (PET), and the sheath component is a copolymer of PET and polybutylene terephthalate (PBT). It will be.

A third component such as a heat-resistant agent, a flame retardant and a matting agent may be mixed with PET to the extent that the original properties of polyester are not impaired.

First, the core component of the fiber is PET having an intrinsic viscosity of 0.8 or more. Here, the intrinsic viscosity is a value measured at 20 ° C. using a mixed solvent of equal weight of phenol and tetrachloroethane. When the intrinsic viscosity is less than 0.8, the fiber is inferior in strength and durability, which is not preferable. Further, the upper limit of the intrinsic viscosity is not particularly limited, but it is preferable to set the intrinsic viscosity in the range of 0.8 to 1.1 in order to perform spinning with good operability. The sheath component is PET / PBT 85 /
It is composed of a copolymer copolymerized at a molar ratio of 15 to 90/10, and the intrinsic viscosity of the copolymer is preferably in the range of 0.7 to 0.85.

By making the sheath component a copolymer composed of PET and PBT in this way, the surface layer of the fiber becomes softer than the inner layer containing PET, and when the fiber is bent, the inner layer is compressed. The required energy is low and the bending rigidity is low. On the other hand, since the inner layer of the fiber is highly oriented, the fiber can have high strength in the fiber axis direction.
The copolymerization ratio of the sheath component PET and PBT is 85/15 to 90 /
It is necessary to set the molar ratio to 10, but PET is more than this range.
When the content is large, the flexibility of the fiber is not sufficiently expressed and the flexural rigidity becomes large, and when the content of PBT is large, the fiber has insufficient strength and durability.

The ratio of the core component to the sheath component is 50/50 by weight.
It should be in the range of 70/30. When the core component is more than this range, the fiber has high bending rigidity, and when the sheath component is more than this range, the strength and durability are insufficient.

The single yarn fineness needs to be 1 to 3d. If the single yarn fineness is larger than 3d, the bending rigidity of the fiber becomes large, and the obtained fabric is not flexible, while if it is smaller than 1d, the strength is poor and the core and sheath components are easily peeled off. The fiber also has poor fatigue resistance.

The total fineness should be in the range of 200 to 500 d. If the total fineness is larger than 500d, the base fabric will lack flexibility when woven at a high density, and if it is smaller than 200d, the base fabric will have a weak tear strength.

The flexural rigidity of the yarn varies depending on the single yarn fineness and the number of filaments, but in the present invention, it is necessary to satisfy the formula (1) in order to impart sufficient flexibility to the woven and knitted fabric. is there.

Further, it is necessary that the tensile strength is 8 g / d or more and the breaking elongation is 15% or more. If the tensile strength is less than 8 g / d, the base fabric will have a weak tear strength,
If the elongation at break is less than 15%, it is not possible to obtain a base fabric having impact resistance capable of withstanding the impact when the airbag is operated.

Next, an example of a method of manufacturing the yarn for airbag of the present invention will be described.

First, using an ordinary extruder type composite spinning machine, spinning was carried out at a spinning temperature in the range of 295 to 305 ° C.,
The yarn immediately after spinning is passed through a heating zone with an ambient temperature of 300 ° C or higher, then cooled by blowing cooling air from the outer periphery of the yarn toward the center, and immediately after cooling and solidification, an oil agent is applied to focus the yarn. To do.

After drawing the bundled yarn, it is stretched to obtain a yarn having a tensile strength of 8 g / d or more, but the stretching process should be continuously performed after spinning in order to improve productivity. Is preferable, so that the take-up speed is in the range of 400 to 600 m / min, and heating steam at a heating temperature of 200 ° C or higher is sprayed or a heat plate is used so that the stress applied to the fiber surface layer during stretching can be reduced. While heating, stretch at a stretch ratio of 4.5 to 5.5.

[0026]

EXAMPLES Next, the present invention will be specifically described by way of examples. In addition, the measuring method of the characteristic value in this invention is as follows.

(A) Tensile strength Using Autograph S-100 manufactured by Shimadzu Corporation, sample length 25c
m, and the pulling speed was 30 cm / min.

(B) Bending rigidity Measurement was carried out using a pure bending tester KES-FB2 manufactured by Kato Tech.

(C) Flexibility JIS L-1096 6.19.1A method (45 ° cantilever method)
It was measured at.

The softness sufficient as a base fabric for an airbag is 60 mm or less.

Examples 1 and 2, Comparative Examples 1 to 5 PET chips having an intrinsic viscosity of 0.9 and PET / PBT copolymer chips having an intrinsic viscosity of 0.75 and a copolymerization ratio shown in Table 1 were used. Each was supplied to a composite melt spinning machine equipped with two extruders and spun at the core-sheath ratio shown in Table 1.

The discharge temperature was 305 ° C., and the spun yarn was
After passing through a heating cylinder with a length of 10 cm that was kept at an ambient temperature of 400 ° C, the air temperature of 20
After being cooled and solidified by blowing cooling air at a temperature of 30 ° C. and a wind speed of 30 m / min, and applying an oil agent, it was taken up by a take-up roller having a surface speed of 480 m / min.

Subsequently, it is sent to a stretching roller having a surface temperature of 220 ° C., and at that time, 400 ° C. between the take-up roller and the stretching roller.
The heated steam was sprayed, the film was drawn at a draw ratio of 5.2 times, subjected to a relaxation treatment of 3% by a relaxation roller having a surface temperature of 160 ° C., and wound at a speed of 2500 m / min.

Table 1 shows the values of total fineness, single yarn fineness, tensile strength, elongation at break, and bending rigidity of the obtained yarn.

Each of the yarns obtained in Examples 1 and 2 had a small bending rigidity, and both the strength and the elongation were values sufficient as a yarn for an airbag.

On the other hand, the yarn obtained in Comparative Example 1 had a low ratio of the core component and thus the strength was low, and the yarn obtained in Comparative Example 2 had a low ratio of the sheath component and thus had a large bending rigidity. .

The yarn obtained in Comparative Example 3 had a sheath component of PBT.
The yarn obtained in Comparative Example 4 has a small single yarn fineness because of a high ratio, and thus the yarn obtained in Comparative Example 5 cannot be collected due to a large number of fluffs during the drawing, and the yarn obtained in Comparative Example 5 has a single yarn fineness. Has a large bending rigidity. Comparative Example 6 The procedure of Example 1 was repeated, except that PET chips having an intrinsic viscosity of 0.9 were supplied to a melt spinning machine equipped with a single extruder to prepare fibers having PET as a single component.

Table 1 shows the values of total fineness, single yarn fineness, tensile strength, elongation at break, and bending rigidity of the obtained yarn.

Since the yarn obtained in Comparative Example 6 was composed of a single component of PET, it had a large bending rigidity.

[0040]

[Table 1]

Example 3, Comparative Example 7 Using the yarns of Example 1 and Comparative Example 6, a woven fabric having a flat design with both warp and weft densities of 48 yarns / 2.54 cm was woven and the flexibility was measured.

Table 2 shows the measured values of the flexibility of the obtained woven fabric.

[0043]

[Table 2]

The woven fabric obtained in Example 3 was excellent in flexibility, but the woven fabric obtained in Comparative Example 7 was made of a yarn having a large bending rigidity, and therefore was not flexible. Inferior, the storability as an airbag base fabric was insufficient.

[0045]

EFFECTS OF THE INVENTION The yarn for an airbag of the present invention can be made into a fabric having the mechanical properties of strength and elongation required for an airbag base fabric and flexibility, if it is woven or knitted. Become.

[0046]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // D01F 6/84 301 H

Claims (1)

[Claims] 1. A core comprising a polyethylene terephthalate having an intrinsic viscosity of 0.8 or more, and a sheath comprising a copolymer of polyethylene terephthalate and polybutylene terephthalate in a molar ratio of 85/15 to 90/10. A yarn consisting of fibers having a core / sheath structure with a weight ratio of / sheath of 50/50 to 70/30, with a single yarn fineness of 1 to 3 d and a total fineness of 200 to
A yarn for an airbag, which has a tensile strength of 500 g, a tensile strength of 8 g / d or more, a breaking elongation of 15% or more, and a bending rigidity in the range of the formula (1). (1) B ≦ 5.5 × 10 ⁻⁶ × TD B: Flexural rigidity (g · cm ² / thread) TD: Total fineness (d)