JP3462914B2 - Thread for airbag - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread for an airbag which can obtain an airbag base fabric having excellent mechanical properties and flexibility. 2. Description of the Related Art At present, airbags used as safety devices for automobiles are mainly formed of a base fabric obtained by coating a synthetic fiber woven fabric using nylon 66 with rubbers. [0003] Airbags, together with shock absorption, are usually
In order to store it in a very small place, it is required to have excellent flexibility. [0004] However, the base fabric in which the synthetic fiber woven fabric is covered with rubber can improve heat resistance and airtightness by covering with rubber, but the base fabric is hardened, so that the storage property is poor. There's a problem. [0005] In order to solve this problem and reduce the manufacturing cost, a non-coated type airbag which is not coated with rubber has recently been developed.
The use of a polyester that is less expensive than 6 and has good heat resistance has been studied. [0006] However, polyester is nylon 6
6 has a drawback of lacking flexibility when woven into a base fabric, especially when woven at high density to increase airtightness, it is more difficult to store compactly. Problem arises. Japanese Patent Application Laid-Open No. Hei 3-167312 proposes a fiber having improved toughness and knot strength as a polyester fiber for an airbag, and an airbag base fabric obtained from this fiber has improved impact resistance and durability. It has excellent properties and the flatness of the base fabric is also improved. [0008] However, the base fabric obtained from these fibers has a drawback that the flexibility is not sufficient, and if the fabric is woven at a high density in order to increase the airtightness, the storability is 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 which is excellent in strength and durability and at the same time. Polyester yarn has not yet been developed. [0010] The present invention solves the above-mentioned problems and provides an airbag capable of obtaining a base cloth having both the mechanical properties and flexibility required for an airbag base cloth. An object of the present invention is to provide a bag thread. Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, have reached the present invention. That is, according to the present invention, the core component has an intrinsic viscosity.
0.8 or more polyethylene terephthalate, wherein the sheath component is composed of a copolymer obtained by copolymerizing polyethylene terephthalate and polybutylene terephthalate in a molar ratio of 85/15 to 90/10, and the core / sheath ratio is 50/50 to 50/50 by weight. A yarn made of fibers having a core / sheath structure of 70/30, having a single yarn fineness of 1 to 3.
d, total fineness is 200-500 d, tensile strength is 8-8.8 g /
d . An airbag yarn characterized by having a breaking elongation of 15 to 17.6% and a bending rigidity in the range of the formula (1). (1) B ≦ 5.5 × 10 ⁻⁶ × TD B: Bending rigidity (g · cm ² / thread) TD: Total fineness (d) (1) B ≦ 5.5 × 10 ⁻⁶ × TD B: Bending Rigidity (g · cm ² / thread) TD: Total fineness (d) Hereinafter, the present invention will be described in detail. The yarn for an airbag of the present invention is composed of a conjugate 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 becomes. To the extent that the intrinsic properties of the polyester are not impaired, a third component such as a heat-resistant agent, a flame retardant, or a matting agent may be mixed with PET. 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 an equal weight of phenol and tetrachloroethane. If the intrinsic viscosity is less than 0.8, the fiber becomes poor in strength and durability, which is not preferable. Although the upper limit of the intrinsic viscosity is not particularly limited, the range of the intrinsic viscosity is preferably set to 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 in 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 of PET and PBT in this way, the surface layer of the fiber becomes more flexible than the inner layer containing PET, and the inner layer is compressed when the fiber is bent. The required energy is small and the bending stiffness is small. 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;
When the amount is too large, the flexibility of the fiber is not sufficiently exhibited, and the bending rigidity is increased. When the amount of PBT is large, the fiber has insufficient strength and durability. The ratio between the core component and the sheath component is 50/50 to 50% by weight.
It must be in the range of 70/30. If the core component is more than this range, the fiber will have high flexural rigidity, and if the sheath component is more than this range, the strength and durability will be insufficient. It is necessary that the fineness of the single yarn is 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. On the other hand, if it is smaller than 1d, the strength is inferior and the core and sheath components are easily peeled off. The fibers also have poor fatigue resistance. The total fineness must be in the range of 200 to 500 d. When the total fineness is larger than 500d, the base fabric lacks flexibility when weaving at a high density, and when the total fineness is smaller than 200d, the base fabric has low tear strength. The value of the bending stiffness of the yarn varies depending on the fineness of the single yarn and the number of filaments. In the present invention, in order to impart sufficient flexibility to the knitted and woven fabric, it is necessary to satisfy the expression (1). is there. Further, it is necessary that the yarn has a tensile strength of 8 to 8.8 g / d and a breaking elongation of 15 to 17.6% . If the tensile strength is less than 8 g / d, the base fabric will have a weak tear strength, and if the elongation at break is less than 15%, it will not be possible to obtain an impact resistant base fabric that can withstand the impact during airbag operation. Next, an example of a method for producing the yarn for an airbag of the present invention will be described. First, using an ordinary extruder-type composite spinning machine, spinning is performed at a spinning temperature in the range of 295 to 305 ° C.
After passing the yarn immediately after spinning through a heating zone with an ambient temperature of 300 ° C or more, the yarn is cooled by blowing cooling air from the outer periphery to the center of the yarn, and is applied with an oil agent immediately after cooling and solidifying to bundle it. I do. After the collected yarn is taken out, the yarn is stretched to obtain a yarn having a tensile strength of 8 to 8.8 g / d. In order to improve the productivity, the stretching process is performed continuously after the spinning. Since it is preferable to carry out the process, the take-up speed is set in the range of 400 to 600 m / min, and a heating temperature of 200 ° C. or more is sprayed, or a heat plate or the like is used so that the stress applied to the fiber surface layer during drawing can be reduced. The film is stretched at a stretching ratio of 4.5 to 5.5 while heating. Next, the present invention will be described specifically with reference to examples. In addition, the measuring method of the characteristic value in this invention is as follows. (A) High elongation Using an Autograph S-100 manufactured by Shimadzu Corporation, sample length 25c
m, and a tensile speed of 30 cm / min. (B) Flexural rigidity The flexural rigidity was measured using a pure bending tester KES-FB2 manufactured by Kato Tech. (C) Flexibility JIS L-1096 6.19.1A method (45 ° cantilever method)
Was measured. The flexibility sufficient as a base fabric for an airbag is 60 mm or less. Examples 1 and 2 and Comparative Examples 1 to 5 A PET chip having an intrinsic viscosity of 0.9 and a PET / PBT copolymer chip having an intrinsic viscosity of 0.75 and a copolymerization ratio shown in Table 1 were used. The extruders were supplied to a composite melt spinning machine equipped with two extruders, and were spun at a core-sheath ratio shown in Table 1. At a discharge temperature of 305 ° C., the spun yarn is
After passing through a 10 cm long heating cylinder maintained at an ambient temperature of 400 ° C., a cylindrical cooling air blowing device is used to adjust the air temperature to 20 ° C.
After cooling and solidifying 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-off roller having a surface speed of 480 m / min. Subsequently, the film is fed to a stretching roller having a surface temperature of 220 ° C., where 400 ° C. is applied between the take-up roller and the stretching roller.
The film was stretched at a stretching ratio of 5.2 times, subjected to a 3% relaxation treatment with 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, breaking elongation and bending rigidity of the obtained yarn. The yarns obtained in Examples 1 and 2 each had a low bending rigidity, and both the strength and the elongation were sufficient values for airbag yarns. On the other hand, the yarn obtained in Comparative Example 1 had a low strength due to a low ratio of the core component, and the yarn obtained in Comparative Example 2 had a high bending rigidity due to a low ratio of the sheath component. . The yarn obtained in Comparative Example 3 was composed of PBT as a sheath component.
Is high, the strength obtained is low, and the yarn obtained in Comparative Example 4 has a small single-fiber fineness. , The bending rigidity was large. Comparative Example 6 The same operation as in Example 1 was carried out except that a PET chip having an intrinsic viscosity of 0.9 was supplied to a melt spinning machine equipped with a single extruder to make a fiber having PET as a single component. Table 1 shows the total fineness, single yarn fineness, tensile strength, elongation at break, and flexural rigidity of the obtained yarn. Since the yarn obtained in Comparative Example 6 was composed of a single component of PET, the yarn had high flexural rigidity. [Table 1] Example 3, Comparative Example 7 Using the yarns of Example 1 and Comparative Example 6, woven fabrics having a flat structure with a warp and weft density of 48 yarns / 2.54 cm were measured, and the flexibility was measured. Table 2 shows the measured values of the flexibility of the obtained woven fabric. [Table 2] The woven fabric obtained in Example 3 was excellent in flexibility, but the woven fabric obtained in Comparative Example 7 was obtained by using a yarn having high flexural rigidity. It was inferior, and the storage property as a base fabric for an airbag was insufficient. The yarn for an airbag of the present invention, when knitted and woven, has a mechanical property of strength and elongation required for an airbag base fabric, and is a fabric having flexibility. Becomes possible. [0046]

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Claims (1)

(57) [Claims 1] A core component is copolymerized with polyethylene terephthalate having an intrinsic viscosity of 0.8 or more, and a sheath component is copolymerized with polyethylene terephthalate and polybutylene terephthalate in a molar ratio of 85/15 to 90/10. A core / sheath fiber having a core / sheath ratio of 50/50 to 70/30 by weight, having a single yarn fineness of 1 to 3d and a total fineness of 200 to Five
00d, tensile strength of 8 to 8.8 g / d , elongation at break of 15 to 17.6
% , An airbag yarn characterized by having a flexural rigidity in the range of the expression (1). (1) B ≦ 5.5 × 10 ⁻⁶ × TD B: Bending rigidity (g · cm ² / thread) TD: Total fineness (d)