JP7560657B2 - Synthetic fiber for airbags and method for manufacturing fabric for airbags using the same - Google Patents

Description

The present invention relates to synthetic fibers for airbags and a method for manufacturing airbag fabrics using the same.

Airbag devices are increasingly being installed in automobiles with the aim of protecting occupants in the event of a car crash. After detecting a car collision, airbags protect occupants by generating high-pressure gas from an inflator and inflating the airbag cushion. To adequately protect occupants, the airbag cushion needs to maintain its inflated state for a long period of time, meaning it needs to be able to retain internal pressure. In recent years, front-third curtain airbags that prevent collisions between the driver and front passenger and pedestrian airbags that protect pedestrians have appeared, but these need to be stored in the narrow space of the seat or bonnet, creating an even greater demand for compact airbag cushions.

The manufacturing process for airbag cushions is mainly divided into four steps: spinning, weaving, sewing, and assembly. Of these, water jet looms (WJL) are often used in the weaving process. In a WJL, water is jetted obliquely from the side onto the yarn that enters from the rear of the nozzle, and the yarn is inserted by riding the water current of the water column that is formed. The weft yarn inserted at the opening of the warp yarn is then held on the opposite side of the nozzle and beaten with a reed to form a woven fabric.

In recent years, in the weaving process by WJL, efforts have been made to increase the weaving speed, improve the efficiency of the process, and reduce the labor required in order to improve productivity.
In the following Patent Document 1, the diffusion of water sprayed from the weft insertion nozzle is restricted, and the weft yarn is allowed to fly stably and reliably, thereby improving the weaving efficiency. On the other hand, depending on the yarn, increasing the weaving speed may cause insufficient flight during weft insertion, resulting in weaving problems.

To solve this problem, the following Patent Document 2 discloses synthetic fibers for airbags that are entangled to improve weft flight during weaving. This allows high-speed weaving at 850 rpm to 1000 rpm, reducing defects in the process. However, all that is mentioned is the number of weaving stops, and there is no mention of the quality of the woven product.

In addition, in the following Patent Document 3, uniform breathability is achieved even in fabrics woven at a high speed of 900 rpm by increasing the intermediate load elastic modulus of synthetic fibers, decreasing the intermediate elastic elongation, improving responsiveness to high speed weft insertion, and suppressing variation in the intermediate load elastic modulus.

JP 2000-34646 A JP 2007-126796 A Patent No. 5253685

As described above, conventional technology has achieved the weaving of fabrics with uniform breathability despite high speed weaving by improving the responsiveness to forces in the direction of weft yarn flight and suppressing variations in responsiveness along the yarn length. The breathability of fabrics is a parameter related to air leakage from the surface of the fabric, and affects the internal pressure retention of airbags. However, when an airbag is deployed, air leakage from the stitching is greater than air leakage from the surface of the fabric, and the effect of fabric breathability on internal pressure retention is negligible.

A parameter related to air leakage from the seams of woven fabric is slippage resistance. If slippage resistance is high, the seams are less likely to become misaligned when stress is applied to the seams during airbag deployment, and the internal pressure is less likely to decrease.

On the other hand, stiffness is a parameter related to the storability of an airbag inside a vehicle. Airbag cushions are folded and stored inside a vehicle as an airbag device, but if the stiffness is high, the airbag cushion will be too bulky after folding and will not be able to be stored properly.

To improve slippage resistance, the usual method is to increase the weave density or crimp rate, but this has the problem of impairing the flexibility of the fabric. For this reason, there is a strong demand for airbag fabrics that are both highly slippage resistant and flexible, and there is a strong demand for airbag yarns that can contribute to achieving both properties at the same time.

Under these circumstances, the problem that the present invention aims to solve is to provide a synthetic fiber for airbags that can be used for both warp and weft yarns when weaving fabrics for airbags with WJL. In particular, the problem is to provide a synthetic fiber for airbags that allows the weft yarn to fly at high speed, reduces uneven tension when it reaches the opposite side of the nozzle, has uniform follow-up to the sprayed water, and also flies at high speed, suppresses variation in quality in the width direction of the fabric (because the instantaneous elastic recovery of polyamide yarn settles in the width direction of the fabric before it is organized), and achieves both high slippage resistance and high flexibility, which are a trade-off in fabrics.

The inventors unexpectedly discovered that in weaving the above-mentioned fabric using WJL, the uniformity of the area of the unentangled parts is important for the uniform flight of the yarn, and the instantaneous hydrophilicity of the yarn is important for its ability to follow the sprayed water, which led to the completion of the present invention.

That is, the present invention is as follows.
[1] A multifilament synthetic fiber for airbags having entangled portions and unentangled portions, characterized in that the water droplet contact angle on the surface of a single yarn is 50 to 75°, and the variation in the area of the unentangled portions per 20 cm is 10% or less in terms of CV value.
[2] The synthetic fiber for airbags according to [1] above, wherein the area of the unentangled parts is in the range of 12.5 to 20 ^cm2 when evaluated every 20 cm in the yarn length direction.
[3] The synthetic fiber for airbags according to [1] or [2] above, wherein the number of single yarns is 60 to 250.
[4] The synthetic fiber for airbags according to any one of [1] to [3] above, having a single yarn fineness of 1 to 7 dtex.
[5] The synthetic fiber for airbags according to any one of [1] to [4] above, wherein the number of single yarns is 200 to 250 and the single yarn fineness is 1.0 dtex to 1.8 dtex.
[6] The synthetic fiber for airbags according to any one of [1] to [5] above, having a degree of entanglement of 10 to 35 pcs/m.
[7] The synthetic fiber for airbags according to any one of [1] to [6] above, wherein the variation in the water droplet contact angle on the surface of a single yarn in the longitudinal direction is 5% or less in terms of CV value.
[8] The synthetic fiber for airbags according to any one of [1] to [7] above, wherein the finishing agent adhesion rate is 0.6 to 1.2% by weight.
[9] The synthetic fiber for airbags according to any one of the above [1] to [8], wherein an anionic surfactant containing a phosphorus atom and/or an anionic surfactant containing a sulfur atom is adhered in an amount of 200 to 500 ppm based on the fiber weight.
[10] The following requirements (1) to (4):
(1) The total fineness is 150 to 800 dtex;
(2) Tenacity is 7.5 to 9 cN/dtex;
(3) Elongation is 15 to 25%; and (4) Boiled water shrinkage is 4 to 11%;
The synthetic fiber for airbags according to any one of the above [1] to [9],
[11] The synthetic fiber winding package for an airbag according to any one of [1] to [10] above, wherein the package width W is 8 to 22 cm.
[12] The steps of:
A step of winding synthetic fibers spun by melt spinning onto a tube using a winding machine equipped with a traverser for swinging the yarn in the tube axial direction, the yarn passing through one or more finishing agent applying (oiling) devices, multi-stage drawing rollers, an entanglement applying device, and one or more yarn path regulating guides provided before and after the entanglement applying device;
wherein in said step, the tension before winding is 0.1 to 0.3 cN, and the short-period oscillation width ratio B in the oscillation of the yarn by a traverser is 0.5 to 5%.
[13] The method for producing a synthetic fiber for airbags according to [12] above, wherein the width W of a package obtained by winding the synthetic fiber around a tube is 8 to 22 cm.
[14] The method for producing a synthetic fiber for an airbag according to [12] or [13] above, wherein the finishing agent is applied by the finishing agent application device so that the anionic surfactant containing a phosphorus atom and/or the anionic surfactant containing a sulfur atom adheres to the fiber in an amount of 200 to 500 ppm based on the fiber weight.
[15] The method for producing a synthetic fiber for an airbag according to any one of [12] to [14], wherein the finishing agent applicator is provided at two or more positions in a yarn path direction, and the oil supply parts of at least two of the finishing agent applicators face each other. [16] The method for producing a synthetic fiber for an airbag according to any one of [12] to [14], comprising the steps of:
Weaving a fabric in a water jet loom at a weaving speed of 800 rpm or more using the synthetic fiber for an airbag according to any one of [1] to [10] as a weft;
A method for producing a fabric for an airbag, comprising:

The synthetic fiber for airbags of the present invention achieves a specific range of variation in the water droplet contact angle on the surface of the single yarn and the area of the unentangled parts, which dramatically improves the weft yarn flight properties (ability to follow the sprayed water) when weaving using WJL, and also provides excellent uniform and linear flight properties (uniform yarn flight properties). These two characteristics make it possible to weave at high speeds without variation in quality across the width of the base fabric.

FIG. 2 is a diagram illustrating the width W of a winding package of synthetic fiber for an airbag. FIG. 2 is a diagram illustrating an example of an apparatus for producing synthetic fibers for airbags. 1 is a diagram for explaining the definition of the short-period oscillation width ratio B and the winding start winding angle θ for determining the method of increasing or decreasing the traverse speed in a winding machine. FIG. FIG. 1 is an explanatory diagram for measuring a water droplet contact angle. FIG. 2 is an explanatory diagram of the definition of the length a and width b of an unentangled portion for determining the area of the unentangled portion and its CV value.

Hereinafter, an embodiment of the present invention will be described in detail.
One embodiment of the present invention is a multifilament synthetic fiber for airbags having entangled portions and unentangled portions, characterized in that the water droplet contact angle on the surface of a single yarn is 50 to 75°, and the variation in the area of the unentangled portions per 20 cm is 10% or less in terms of CV value.

The water droplet contact angle on the surface of a single yarn of the synthetic fiber for airbags in this embodiment is from 50° to 75°. The water droplet contact angle refers to the maximum contact angle within 100 ms (one frame of a video is 8 ms) when a certain amount of water droplet is attached to a single yarn of the synthetic fiber for airbags and the contact angle is observed over time from the side as shown in Figure 4.
If the water droplet contact angle is 50° or more, the surface tension of the jet water acts appropriately within the yarn during weft insertion, allowing the yarn to fly without coming apart. By preventing the yarn from coming apart, the air resistance experienced by the yarn during flight is reduced, improving the weft flight property and stabilizing the weft insertion property at high speed. By stabilizing the weft insertion behavior, the weft yarn is woven into the warp yarn after the instantaneous elastic recovery has settled, which contributes to the uniformity of the physical properties of the airbag fabric during high-speed weaving. In addition, the jet water contained in the yarn becomes uniform, resulting in uniform flight, which contributes to the uniformity of the physical properties of the fabric. In addition, if the contact angle is 75° or less, the hydrophilicity of the yarn is increased and the ability to follow the jet water is improved, which causes a bump-like phenomenon (explosion phenomenon of the jet water), causing the jet water to scatter and the yarn to not reach the opposite nozzle side, resulting in insufficient flight and weaving troubles. A low water droplet contact angle allows the yarn to quickly absorb the jet of water in milliseconds, which quickly widens the unentangled parts and makes the water more efficient to fly, contributing to uniform fabric properties for the same reasons as above. The lower the water droplet contact angle α, the more uniform the airbag fabric properties. The water droplet contact angle is more preferably 50 to 70°, and even more preferably 50 to 65°.

In this embodiment, the variation in the water droplet contact angle on the surface of a single yarn of the synthetic fiber for airbags in the yarn length direction is 5% or less in CV value (coefficient of variation). If the CV value is 5% or less, the adhesion of the finishing agent to the single yarn is uniform in the yarn length direction, the amount of water contained in the yarn at the time of weft insertion is uniform, there is no variation in the flying property, and the variation in the ratio of slip resistance to bending resistance (EC/V) can be reduced, that is, a woven fabric of uniform quality, particularly a woven fabric of uniform quality in the width direction of the base fabric, can be obtained. The CV value is preferably 4.5% or less. The lower limit of the CV value is not particularly limited, but may be 1% or more as an economically feasible range.

In this embodiment, the variation in the area of the unentangled portion of the synthetic fiber for airbags every 20 cm is 10% or less in terms of CV value (coefficient of variation). If the CV value is 10% or less, the length a of the unentangled portion and the width b of the spread of the yarn due to the surface tension of the finishing agent are uniform, as shown in FIG. 5, and the amount of water contained in the yarn during weft insertion when weaving with WJL is uniform, eliminating the variation in the flying property and reducing the variation in the ratio of slip resistance to bending resistance (EC/V), that is, a woven fabric of uniform quality, particularly a woven fabric of uniform quality in the width direction of the base fabric, can be obtained. The CV value is preferably 8% or less, more preferably 7% or less. The lower limit of the CV value is not particularly limited, but may be 3% or more as an economically feasible range. If the appearance of the unentangled portion is uniform anywhere when measuring a 20 cm yarn length, the flying property when sprayed with water will be uniform.

In the present embodiment, the area of the unentangled portions of the synthetic fiber for airbags is preferably 12.5 to 20 ^cm2 when evaluated every 20 cm in the yarn length direction. If the area of the unentangled portions is 12.5 ^cm2 or more, the yarns will be able to fully contain water, the weft will fly well, and the loom will be prevented from stopping. On the other hand, if the area of the unentangled portions is 20 ^cm2 or less, the length of the entangled portions can be made appropriate, the yarns will not come apart, and the loom will be prevented from stopping. The area of the unentangled portions is more preferably 14 to 17.5 ^cm2 when evaluated every 20 cm in the yarn length direction.

In the present embodiment, the synthetic fiber for airbags preferably has an anionic surfactant containing phosphorus atoms and/or an anionic surfactant containing sulfur atoms attached in an amount of 200 to 500 ppm relative to the fiber weight. By containing 200 ppm or more of ionic surfactant, the water droplet contact angle is sufficiently low, the yarn becomes more hydrophilic, and the weft thread flying property is improved by improving the tracking ability of the sprayed water during weft insertion in the weaving process. On the other hand, if the attachment rate is 500 ppm or less, the water droplet contact angle is too small and the yarn does not break apart when the weft thread flies in weaving. The attachment rate of the anionic surfactant relative to the fiber weight is more preferably 250 to 500 ppm, and even more preferably 300 ppm to 500 ppm. The anionic surfactant containing phosphorus atoms is not particularly limited, but examples thereof include metal salts or amine salts of alkyl phosphate esters (hereinafter abbreviated as phosphates), and metal salts or amine salts of polyoxyethylene alkyl phosphates. More specifically, examples of the surfactant include potassium lauryl phosphate, sodium lauryl phosphate, potassium octyl phosphate, and sodium octyl phosphate. The anionic surfactant containing a sulfur atom is not particularly limited, but examples thereof include alkanesulfonates. The method of attaching the ionic surfactant is not particularly limited, but it is preferable to attach it by mixing it into the finishing agent.

In this embodiment, the degree of entanglement of the synthetic fiber for airbags is preferably 10 to 35 pieces/m as measured by the water immersion method as shown in Figure 5. If the degree of entanglement is 10 pieces/m or more, the bundling required for the warp yarn during weaving is fully satisfied, and there is no decrease in weaving efficiency or loss of woven quality. On the other hand, if the number of entanglements is 35 pieces/m or less, the area of the non-entangled part becomes an appropriate size, the flying property of the weft yarn is improved, and there is little variation in the single yarn length in the length direction of the yarn, which suppresses the occurrence of yarn breakage and fluff during weaving and prevents the loom from stopping. The degree of entanglement is more preferably 15 to 30 pieces/m.

The synthetic fiber for airbags in this embodiment is a multifilament, and preferably has 60 to 250 single threads. If the number of single threads is 60 or more, the number is sufficient to form an entanglement, and there is no variation in the number of single threads due to the inability to form an entanglement. The number of single threads is more preferably 120 or more. On the other hand, if the number of single threads is 250 or less, the efficiency of the use of air energy for imparting entanglement is good, and uniform and good entanglement can be achieved. The number of single threads is more preferably 200 or less.

The single yarn fineness of the multifilament synthetic fiber for airbags of this embodiment is preferably 1 to 7 dtex. If the single yarn fineness is 1 dtex or more, the tensile properties such as single yarn toughness are sufficient, and the generation of fuzz during the spinning process can be suppressed. On the other hand, if the single yarn fineness is 7 dtex or less, the yarn can be swirled with less energy during the entanglement process, and the intended entanglement state can be obtained. Furthermore, if the single yarn fineness is 4 dtex or less, the gap between the single yarns is reduced, so that the effect of the surface tension of the sprayed water in the yarn during weft insertion is greater, and the twisted yarn can fly without coming apart. From the viewpoint of obtaining sufficient tensile properties, the single yarn fineness is more preferably 2 to 7 dtex, and from the viewpoint of flight property during weft insertion, the single yarn fineness is more preferably 1 to 4 dtex, even more preferably 1 to 3 dtex, and even more preferably 1.0 dtex to 1.8 dtex.

In the multifilament synthetic fiber for airbags of this embodiment, it is preferable that the number of single yarns is 200 to 250 and the single yarn fineness is 1.0 dtex or more and 1.8 dtex or less. If the single yarn fineness is 1.0 dtex or more and 1.8 dtex or less, it has a higher degree of flexibility when woven. If the number of single yarns is 200 to 250, even if the single yarn fineness is a low fineness of 1.0 dtex or more and 1.8 dtex or less, it has sufficient mechanical properties as a multifilament fiber.

The multifilament synthetic fiber for airbags of this embodiment preferably has physical properties of a total fineness of 150 to 800 dtex, a strength of 7.5 to 9 cN/dtex, an elongation of 15 to 25%, and a boiling water shrinkage of 4 to 11%.
If the total fineness is 150 dtex or more, the fabric has sufficient mechanical properties when made into an airbag fabric. On the other hand, if the total fineness is 800 dtex or less, it becomes easy to impart bundling properties in the entanglement imparting step. In other words, when the fineness is large, in order to impart appropriate entanglement, the air pressure or air flow rate required for yarn rotation must be significantly increased, which not only increases the cost of additional utilities but also makes the yarn susceptible to damage at the entanglement nozzle, causing fluffing and reducing the yarn quality. However, if the total fineness is 800 dtex or less, this does not occur. The total fineness is more preferably 200 to 550 dtex.

The (tensile) strength is preferably 7.5 to 9.0 cN/dtex. A high tensile strength of 7.5 cN/dtex or more contributes to improving the mechanical properties of the fabric. The tensile strength is more preferably 8.0 cN/dtex or more. Taking into account other properties, production costs, etc., the tensile strength of synthetic fibers for airbags is substantially 9.0 cN/dtex or less.

It is preferable that the elongation is 15 to 25%. If the elongation is 15% or more, excessive stress will not be applied to the boundary between the inflatable and non-inflatable parts during deployment, which may result in breakage. Furthermore, there is a trade-off between elongation and strength, and it is preferable that the elongation is 25% or less in order to achieve a balance with strength.

The boiling water shrinkage rate is preferably in the range of 4 to 11%. If the boiling water shrinkage rate is 4% or more, the fabric can be shrunk in the processing step after weaving, which contributes to making the finished fabric denser. A boiling water shrinkage rate of 6% or more is more preferable. If the boiling water shrinkage rate is 6% or more, the fabric can be shrunk in the processing step after weaving, which contributes to equalizing the variation in the mechanical properties of the fabric. A boiling water shrinkage rate of 7% or more is particularly preferable. If the boiling water shrinkage rate is 11% or less, when the fabric is woven, excessive shrinkage will not cause imbalance in the warp and weft directions, which will induce opening of the mesh. A boiling water shrinkage rate of 9.5% or less is more preferable, and 9% or less is even more preferable.

Another embodiment of the present invention is the above-mentioned synthetic airbag fiber winding package, wherein the width W of the package is 8 to 22 cm.
Such a winding package (a fiber packaging form in which the fibers are wound around a paper tube or the like by a winding machine) preferably has a package width W of 8 to 22 cm as shown in Figure 1. If W is 8 cm or more, the shape is stable and transportation efficiency is also good. On the other hand, if the width W is 22 cm or less, the variation in the area of the unentangled parts due to the difference in tension between the center and both ends in the width direction of the package during winding is reduced. W is more preferably 8 to 18 cm.

The synthetic fibers constituting the synthetic fiber for airbags of this embodiment are preferably long fibers made of polyamide or polyester multifilaments. Polyamide fibers are particularly preferred, as they have a high melting point and a large heat capacity, and therefore have excellent heat resistance. For example, fibers made of polyamide 6, polyamide 6.6, polyamide 11, polyamide 12, polyamide 6.10, polyamide 6.12, polyamide 4.6, copolymers thereof, and mixtures thereof may be mentioned. Among them, polyamide 6.6 fibers made mainly of polyhexamethylene adipamide fibers are preferred. Polyhexamethylene adipamide refers to polyamide fibers made of 100% hexamethylene diamine and adipic acid and having a melting point of 250°C or higher. The polyamide 6.6 fibers of the present invention are made of polyhexamethylene adipamide, polyamide 8, polyamide 6, etc., within a range in which the melting point is not less than 250°C. Alternatively, fibers made of a copolymer or blend of polyamide I, polyamide 10, polyamide 6.T, etc. may be used.

Yet another embodiment of the present invention is a method for producing a process comprising the steps of:
A step of winding synthetic fibers spun by melt spinning onto a tube using a winding machine equipped with a traverser for swinging the yarn in the tube axial direction, the yarn passing through one or more finishing agent applying (oiling) devices, multi-stage drawing rollers, an entanglement applying device, and one or more yarn path regulating guides provided before and after the entanglement applying device;
wherein the tension before winding in the process is 0.1 to 0.3 cN, and the short-period oscillation width ratio B in the oscillation of the yarn by a traverser is 0.5 to 5%.

A method for producing a winding package of synthetic fibers for an airbag according to this embodiment will now be described.
FIG. 2 is an explanatory diagram showing an example of equipment for producing the synthetic fiber for airbags according to the present embodiment. First, the molten polymer is uniformly heated by a part of the spinning machine called the spin head 3, and is spun out from the spinneret 4. The spun polymer is solidified by cold air from the cooling chamber 5 to form a yarn. The yarn gathered at each end is then given a finishing agent by the oiling device 6, and then proceeds to a drawing process by a group of rollers consisting of a take-up roller 7 and a first roller 8 to a fourth roller 11. That is, the yarn is taken up at a predetermined speed by the roller 7, and then guided to the first-stage roller 8 with a slight tension, and drawn from the first-stage roller 8 by multiple heated drawing rollers 9, 10, and 11. The yarn is then supplied to an entanglement imparting device 13 through a yarn path regulating guide 12, and wound up by a winder 14 through the yarn path regulating guide 12.

The oiling device 6 is generally of the roll type or nozzle type. The oiling device 6 may have one or more, but it is preferable that there are two or more at different positions in the yarn path direction, and that at least two of the oiling parts face each other. In particular, when the single yarn fineness is 1.0 to 1.8 dtex, the vibration of the yarn during the process of solidifying it with cold air from the cooling chamber 5 is transmitted to the oiling process, causing the contact of the yarn with the oiling device 6 to become disturbed, and the application of the finishing agent tends to become uneven. By providing two or more oiling devices at different positions in the yarn path direction and having at least two of the oiling parts face each other, the contact disturbance of the yarn with the oiling device can be suppressed, and the finishing agent can be applied uniformly even when the single yarn fineness is 1.0 to 1.8 dtex, and the variation in the water droplet contact angle on the single yarn surface in the yarn length direction can be suppressed.

The adhesion rate of the finishing agent applied to the synthetic fibers by the oiling device 6 is preferably in the range of 0.6 to 1.2% by weight. Yarn with an adhesion rate of finishing agent of 1.2% by weight or less rarely has stickiness (tackiness) that makes it difficult for the weft yarn to fly. A finishing agent adhesion rate of 0.6% by weight or more can suppress the occurrence of fuzz in the single yarn during drawing in the spinning process.

In addition to the ionic surfactants mentioned above, the components of the finishing agent applied to the synthetic fibers by the oiling device 6 preferably contain components that are excellent in smoothness and heat resistance so that the yarn can be smoothly stretched during the spinning process, from the viewpoints of yarn quality and industrial material applications.

The component as a smoothing agent is preferably an ester compound, and preferably contains at least one ester compound selected from an ester compound having three or more ester bonds in the molecule and an ester compound having a sulfur element in the molecule.
Examples of the ester compound having a sulfur element in the molecule include (1) ester compounds of a divalent carboxylic acid and a monohydric alcohol, such as dialkylthiodipropionate, and (2) ester compounds of a monovalent carboxylic acid and a monohydric alcohol, such as alkylmercaptopropionate.

Examples of ester compounds having three or more ester bonds in the molecule include (3) ester compounds of polyhydric alcohols and monovalent carboxylic acids, such as trimethylolpropane trialchelate, glycerin trifatty acid ester, pentaerythritol tetrafatty acid ester, and trimethylolpropane fatty acid ester; (4) ester compounds of polyhydric carboxylic acids and monovalent alcohols, such as trialkyl trimellitate and triethyl citrate; and (5) natural fats and oils, such as castor oil, palm oil, and rapeseed oil. These components may be used alone or in combination of two or more.

The nonionic surfactant can be used as an emulsifying agent and an agent for adjusting friction.
For example, (1) polyoxyalkylene polyhydric alcohol fatty acid ester-type nonionic surfactants such as ether ester compounds obtained by condensing at least one compound selected from polyethylene glycol dialkylate, polyoxyethylene sorbitan monoalkylate, polyoxybutylene sorbitan trialchelate, polyoxypropylene castor oil, polyoxyethylene hydrogenated castor oil, polyoxyethylene propylene hydrogenated castor oil trialchelate, polyoxyethylene hydrogenated castor oil trialchelate, ethylene oxide (hereinafter referred to as EO) adduct of castor oil, and EO adduct of hydrogenated castor oil with monocarboxylic acid and dicarboxylic acid; (2) at least one compound selected from organic acid, organic alcohol, organic amine, and organic amide with carbonyl group; Compounds having alkylene oxides with prime numbers of 2 to 4 added thereto, more specifically, ether-type nonionic surfactants such as polyoxyethylene fatty acid esters, polyoxyethylene fatty acid ester methyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, polyoxyethylene polyoxypropylene nonylphenyl ethers, polyoxyethylene alkylamino ethers, and polyoxyethylene fatty acid amide ethers, (3) polyhydric alcohol partial ester-type nonionic surfactants such as sorbitan mono fatty acid esters, sorbitan tri fatty acid esters, and glycerin mono fatty acid esters, and (4) alkylamide-type nonionic surfactants such as diethanolamine mono fatty acid amides, etc. These components may be used alone or in combination of two or more.
The finishing agent may be diluted with mineral oil or may be made into a water-based emulsion. Although there is no particular limitation, it is preferable to use it as an emulsion when considering compatibility with water in the subsequent process.

The entanglement device 13 is provided at its upstream and downstream with yarn path control guides 12 for stabilizing the yarn running. It is preferable to maintain the yarn running angle, determined by these and the entanglement nozzle of the entanglement device, in the range of 1 to 10° in order to obtain synthetic fibers for airbags with little variation. It is preferable to set the distance between the two yarn path control guides 12 to 50 to 90 mm in order to obtain a suitable non-entangled area. The entanglement device 13 may be a known device that injects compressed fluid onto the yarns using an entanglement nozzle, but it is preferable to supply the compressed fluid to the yarns with an energy of 0.5 to 3.5 kW. The supply energy of the compressed fluid can be calculated by the product of the supply pressure (Mpa) and the usage flow rate (Nm ³ /hr), and the above supply energy range can be satisfied by arbitrarily selecting the supply pressure and the fluid inlet diameter of the entanglement nozzle. Furthermore, it is preferable to adjust the speed ratio between the fourth roller 11 and the winder and the temperature of the fourth roller 11 within the above range, and set the winding tension (tension before winding) between the fourth roller 11 and the winder 14 in the range of 0.1 to 0.3 cN/dtex. If the winding tension is 0.1 cN or more, there is no yarn drop and the package shape is stable. In addition, the package density increases and the transport efficiency increases. On the other hand, if the tension before winding is 0.3 cN or less, the yarn is sufficiently entangled, the entangled portion is stable and there is little variation, and at the same time, tension fluctuation when the package is released can be minimized, and the package unwinding property is excellent.

The synthetic fiber for airbags in this embodiment is wound around a paper tube or the like by a winding machine 14. At that time, the yarn is oscillated in the axial direction of the paper tube by a traverser, and oscillated left and right within the winding package width to be packaged in a cylindrical shape. If the angle between the direction in which the traversed fiber yarn is wound up on the drum and the plane perpendicular to the rotation axis of the package drum is the twill angle θ, then (traverse speed) = (winding speed) x (tan θ), and the traverse speed is controlled by setting the twill angle. In controlling the traverse speed, it is preferable to apply a short-period oscillation means such that the speed at which the yarn is oscillated left and right within the winding width satisfies the short-period oscillation width ratio B of 0.5 to 5%, in addition to setting the twill angle.

The short-period oscillation width ratio B is defined in FIG. 3. B can be set on the traverser control application. The twill angle θ usually changes with each winding time, but by setting B, it is possible to make fine changes in the twill angle at a certain winding time. For example, if the twill angle at the start of winding is 10°, setting B to 1% allows a short-period twill angle change of -0.1 to 0.1° (±1% of 10°) to be made to the twill angle that changes over time. In this case, a short period refers to a period of 0.1 to 2 seconds. B is set to prevent ribbon winding, but the inventor has found that by performing such a variable traverse, it is possible to suppress the fluctuation in the winding tension of the yarn due to traversing, and to obtain a uniform synthetic fiber for airbags with little variation in the area of the non-entangled part without impairing the entanglement. If the short-period oscillation width ratio B is set to 0.5% or more, ribbon winding can be avoided and tension fluctuations in winding can be suppressed. On the other hand, if B is set to 5% or less, the winding diameter does not vary depending on the magnitude of the winding angle in a short period, and the yarn does not fall off.

Yet another embodiment of the present invention is a method for producing a process comprising the steps of:
weaving a fabric using the synthetic fiber for an airbag as a weft yarn in a water jet loom at a weaving speed of 800 rpm or more;
The method for producing a fabric for an airbag includes the steps of:
In order to obtain a synthetic fiber for airbags with good flying properties in WJL, it is important to improve the entanglement uniformity by adjusting the traverse conditions as described above, and to improve the hydrophilicity of the yarn by selecting a finishing agent.

The synthetic fiber for airbags of this embodiment is suitable for use as a weft thread in weaving with a WJL, particularly in high-speed weaving at 800 rpm or more, and in weaving with a wide loom of 2 m or more. The synthetic fiber for airbags of this embodiment can also be suitably used as a warp thread for weaving. In addition, a sizing treatment may be performed on the warp thread before weaving to improve its smoothness. In addition, after weaving, oil may be removed in a refining process, or the refining process may be omitted. The woven fabric may be shrunk by treatment with hot water or hot air. In this shrinkage process, the tension in the width direction or the reverse length direction of the woven fabric may be controlled, or the dimensional change rate may be adjusted.

The synthetic fiber for airbags of this embodiment is suitable for weaving into a high-density fabric using the same as weaving yarn, and it is preferable to use the synthetic fiber for airbags in a fabric having a cover factor of 2000 to 2500. If the cover factor is 2000 or more, sufficient strength and low air permeability can be ensured as a fabric for airbags. On the other hand, if the cover factor is 2500 or less, sufficient flexibility, thinness, and lightness can be achieved. The cover factor is more preferably 2200 to 2500. The cover factor is {warp density (pieces/2.54 cm) x (warp fineness (dtex)) ^1/2 + weft density (pieces/2.54 cm) x (weft fineness (dtex)) ^1/2 }.

The airbag fabric using the synthetic fiber of this embodiment preferably has a ratio of slippage resistance to bending resistance (EC/V) of 25 N/N or more. If the EC/V is 25 N/N or more, the fabric will have sufficient low breathability and flexibility for use in airbags. The EC/V is more preferably 35 N/N or more, and even more preferably 45 N/N or more.

In the airbag fabric using the synthetic airbag fiber of this embodiment, it is preferable that the variation in the ratio of slippage resistance to bending resistance (EC/V) is 20% or less in CV value. If the EC/V CV value is 20% or less, the variation in the width direction of the fabric is small, the physical properties of the base fabric are stabilized, and the airbag fabric has high slippage resistance and good flexibility. Therefore, no matter which part of the fabric the airbag parts are cut from, they have the same physical properties, and the reliability of the airbag is improved. The EC/V CV value is more preferably 17.5% or less, and even more preferably 15% or less.

The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these examples. In addition, the finishing agent composition, definitions of physical properties, and measurement methods used in the following examples are as follows.

(1) Preparation of Finishing Agent The finishing agent used in the spinning oil was prepared by the following method.
First, a base composition A was prepared. The composition A had the following components:
Dialkyl (C12-18) thiodipropionate: 40 parts by weight Ethylene oxide 25 mole adduct of hydrogenated castor oil: 30 parts by weight Propylene oxide/ethylene oxide alkyl (C12-18) polyether: 30 parts by weight An ionic surfactant, alkyl (C12-16) phosphate amine salt, was added to the above base composition A so as to obtain the "ionic surfactant content (wt%) in the finishing agent" shown in Tables 1 and 2 below, to adjust the finishing agent. Water was added so that the finishing agent content was 22 wt% to prepare an emulsion liquid.

(2) Water droplet contact angle (°)
The water droplet contact angle was measured using an automatic contact angle meter ("MCA-J" manufactured by Kyowa Interface Science Co., Ltd.). Figure 4 is an explanatory diagram of the measurement of the water droplet contact angle. The measurement conditions were: temperature In the air at 25°C and 50% humidity, the single yarn was fixed between the measuring jigs, 20 pL of water at 24°C was placed on the single yarn, and the state of the water droplet was recorded from the side with a camera to measure the contact angle. The contact angle α decreases over time (as the water becomes accustomed to the thread), but in order to confirm the instantaneous water accustoming of the thread, the contact angle α is measured within 100 ms (one frame of the video is 8 ms). This procedure was repeated for another single yarn, and the average value of all five measurements was taken as the water droplet contact angle of each single yarn.

(3) Coefficient of variation of water droplet contact angle in the thread length direction, CV
The water droplet contact angle was measured at 10 points at 5 cm intervals for one single yarn, and the CV value of the single yarn was calculated as follows.
CV (%) = (s/X) x 100
where s is the standard deviation and X is the mean.
This procedure was repeated for five other single yarns, and the average CV value of each single yarn was taken as the coefficient of variation CV of the water droplet contact angle in the yarn length direction. A higher CV value indicates a larger variation.

(4) Degree of entanglement (pieces/m)
The water bath for measuring the degree of entanglement was 1.2 m long, 20 cm wide, and 15 cm high (depth), with white lines 10 cm apart from each end, i.e., 1 m apart. The water supplied from the bath is drained by overflow. In other words, the water in the measurement bath is constantly renewed by supplying new water at a flow rate of about 500 cc/min. The cut yarn is held at both ends and immersed in a measurement bath under a tension of about 10 cN, and when it becomes relaxed on the water surface, the number of entanglements between the white lines (pieces/m) is visually read. These measurements are repeated 50 times and the average value is evaluated.

(5) Unentangled area (cm ² )
As in (4) above, the yarn is immersed in the measurement bath, and the length a of the unentangled portion of the yarn spread on the water surface and the width b of the unentangled portion are measured on a scale as shown in FIG. The area of the unentangled part that spreads above the water surface in a 20 cm section of the yarn length is totaled as one measurement, and this measurement is repeated 25 times for different 20 cm sections each time. The average value was calculated.

(6) Coefficient of variation of unentangled area CV
The area of the unentangled portion measured in (5) above was calculated by the following formula. A higher CV value indicates a larger variation.
CV (%) = (s/X) x 100
where s is the standard deviation and X is the mean.

(7) Fineness: Measured according to JIS L 1017 8.3a. A 50 m sample was taken from the winding package using a measuring machine with a frame circumference of 1.25 m.

(8) Strength (cN/dtex), elongation (%)
The sample was left for 12 hours under standard conditions (20° C., 65%) and then measured according to JIS L 1017 8.5a with a sample length of 250 mm and a tensile speed of 300 mm/min.

(9) Boiling water shrinkage rate (%)
The measurement was performed according to JIS L 1017 8.14. After immersion in boiling water, the sample was left to stand for 12 hours in a room under standard conditions (20° C., 65%).

(10) Finishing agent adhesion rate (wt%)
The measurement was performed according to JIS L 1017 8.16b. Cyclohexane was used as the extraction solvent.

(11) Ionic surfactant adhesion rate (ppm)
This was calculated from the value measured in (10) above (finishing agent adhesion rate (wt %)) and the ionic surfactant concentration in the finishing agent (ionic surfactant content (%) in the finishing agent).

(12) Weft slippage resistance EC (N)
The process of taking samples at five locations in the width direction of the base fabric was repeated five times in the length direction of the base fabric, i.e., a total of 25 samples were taken. The weft slippage resistance (N) of these samples was measured according to ASTM D6479, and the average value was calculated.

(13) Base fabric stiffness V (N)
In the above (12) weft slippage resistance EC test, samples were taken from adjacent parts of the sample, and the fabric stiffness (N) of the obtained 25 samples was measured according to ASTM D4032, and the average value was calculated. .

[Example 1]
2, nylon 66 polymer having a relative viscosity of 80 in 90% formic acid obtained by a conventional polymerization method was melted at 300°C, uniformly heated by a spin head 3, discharged from a spinneret 4 having 136 holes, and wound up by a direct spinning and drawing process to spin a polyamide 66 fiber of 470 dtex and 136 filaments. That is, the discharged nylon 66 polymer was cooled and solidified in a cold air chamber 5 to form a yarn, which was then passed through an oil supplying device 6, a take-up roller 7, a first roller 8 to a fourth roller 11 in this order, the yarn running was stabilized by a yarn path regulating guide 12, the yarn was entangled by an entanglement imparting device 13, passed through the yarn path regulating guide 12, and wound up by a winder 14.

In the oiling process, a finishing agent was applied in one finishing agent application device with a composition such that the adhesion rate was 0.7% and the adhesion rate of the ionic surfactant was 350 ppm. Compressed air was applied to the interlacing device 13 at 0.5 MPa, and the air supply energy was 1.2 kW. The distance between the yarn path control guides 12 was 7.3 cm. The winding tension was adjusted to 0.19 cN/dtex. The winding conditions were a short-period oscillation width ratio B of 4.0%, a winding start twill angle of 7.8°, and a package width W of 16 cm. The physical properties of the obtained polyamide 66 fiber are shown in Table 1 below.

The obtained polyamide 66 fibers were plain woven at 900 rpm using a WJL to obtain a woven fabric. The obtained woven fabric was refined by continuous scouring at 80°C, and heat set in a tenter at 170°C with an overfeed of 4% and a width of 1% to obtain a woven fabric with a warp and weft density of 53 x 53 threads per 2.54 cm. The cover factor was 2298. The slippage resistance and stiffness of the base fabric of this woven fabric were evaluated. The evaluation results are shown in Table 1 below. The water droplet contact angle was at an appropriate level, the coefficient of variation of the unentangled area was small, and the coefficient of variation of EC/V was small, resulting in a woven fabric with little variation.

[Example 2]
Except for changing the adhesion rate of the ionic surfactant to 490 ppm in the oiling step, the same procedure as in Example 1 was carried out. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in the following Table 1. The water droplet contact angle was at an appropriate level, and the coefficient of variation of EC/V was small, resulting in a woven fabric with little variation.

[Example 3]
Except for changing the adhesion rate of the ionic surfactant to 210 ppm in the oiling step, the same procedure as in Example 1 was carried out. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in the following Table 1. The water drop contact angle was slightly large even within an appropriate range, and the coefficient of variation of EC/V was somewhat large, resulting in a woven fabric with some variation.

[Example 4]
The same procedure as in Example 1 was carried out except that in the oiling process, the adhesion rate of the ionic surfactant was set to 490 ppm, and in the winding process, the package width W was set to 8.5 cm. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in the following Table 1. The water drop contact angle was at an appropriate level, and the coefficient of variation of the unentangled part area and the coefficient of variation of EC/V were small, resulting in a woven fabric with little variation.

[Example 5]
The same procedure as in Example 1 was carried out except that in the winding process, the short cycle oscillation width ratio B was 1.5% and the package width W was 8.5 cm. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in the following Table 1. The coefficient of variation of the unentangled part area and the coefficient of variation of EC/V were small, resulting in a woven fabric with little variation.

[Example 6]
The same procedure as in Example 1 was carried out except that in the winding process, the short cycle oscillation width ratio B was set to 0.8% and the package width W was set to 8.5 cm. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in the following Table 1. The coefficient of variation of the unentangled part area was slightly large, and the coefficient of variation of EC/V was slightly large, resulting in a woven fabric with some variation.

[Example 7]
The same procedure as in Example 1 was carried out except that the package width W in the winding process was set to 19.0 cm. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in the following Table 1. The coefficient of variation of the unentangled part area was slightly large, and the coefficient of variation of EC/V was slightly large, resulting in a woven fabric with some variation.

[Example 8]
The same procedure as in Example 1 was carried out, except that in the entanglement step, the distance between the yarn path regulating guides 12 was set to 7.8 cm. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in the following Table 1. The woven fabric had a large unentangled part area, a small coefficient of variation of EC/V, and little variation.

[Example 9]
The same procedure as in Example 1 was carried out, except that the air supply energy in the entanglement step was 0.7 kW. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in Table 2. The woven fabric had a large unentangled area, a small coefficient of variation of EC/V, and little variation.

[Example 10]
The same procedure as in Example 1 was carried out, except that in the polymer discharge step, the number of holes in the spinneret 4 was set to 72, and polyamide 66 fiber of 470 dtex and 72 filaments was spun. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in Table 2 below. The water drop contact angle was somewhat large, and the coefficient of variation of EC/V was somewhat large, resulting in a woven fabric with some variation.

[Example 11]
In the polymer discharge step, polyamide 66 fibers of 350 dtex and 136 filaments were spun. In the weaving step, the weaving density of the warp and weft yarns was 60 x 60 yarns per 2.54 cm, and a woven fabric with a cover factor of 2245 was obtained. The same procedures as in Example 1 were carried out except for the above discharge and weaving steps. The physical properties of the obtained polyamide 66 fibers and the evaluation results of the woven fabric are shown in Table 2 below. The water droplet contact angle was at an appropriate level, the coefficient of variation of the unentangled part area was small, and the coefficient of variation of EC/V was small, resulting in a woven fabric with little variation.

[Example 12]
In the polymer discharge step, the number of holes in the spinneret 4 was set to 216, and polyamide 66 fiber of 350 dtex and 216 filaments was spun. The procedure was the same as in Example 11 except for the above-mentioned discharge step. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in Table 2 below. The water droplet contact angle had a large variation, and the coefficient of variation of EC/V was somewhat large, resulting in a woven fabric with some variation.

[Example 13]
In the polymer discharge step, the number of holes in the spinneret 4 was set to 216, and in the oiling step, two oiling devices were installed at different positions in the yarn path direction, and the oiling parts were directed opposite to each other to apply a finishing agent, thereby spinning a polyamide 66 fiber of 350 dtex and 216 filaments. The same procedure as in Example 11 was carried out except for the above-mentioned discharge step and oiling step. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in Table 2 below. The water droplet contact angle was at an appropriate level, and although the single yarn was thin, the variation in the water droplet contact angle was small, the coefficient of variation of the unentangled part area was small, and the coefficient of variation of EC/V was small, resulting in a woven fabric with little variation.

[Example 14]
In the polymer discharge step, the number of holes in the spinneret 4 was set to 216, and polyamide 66 fibers of 235 dtex and 216 filaments were spun. In the weaving step, the weaving density of the warp and weft yarns was set to 72 x 72 threads per 2.54 cm, and a woven fabric with a cover factor of 2207 was obtained. The same procedures as in Example 1 were carried out except for the above discharge step and weaving step. The physical properties of the obtained polyamide 66 fibers and the evaluation results of the woven fabric are shown in Table 2 below. The variation in water droplet contact angle was large, and the coefficient of variation of EC/V was somewhat large, resulting in a woven fabric with some variation.

[Example 15]
In the polymer discharge step, the number of holes in the spinneret 4 was set to 216, and in the oiling step, two oiling devices were installed at different positions in the yarn path direction, and the oiling parts were directed opposite to each other to apply a finishing agent, thereby spinning a polyamide 66 fiber of 235 dtex and 216 filaments. The procedure was the same as in Example 14 except for the above-mentioned oiling step. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in Table 2 below. The water droplet contact angle was at an appropriate level, and although the single yarn was thin, the variation in the water droplet contact angle was small, the coefficient of variation of the unentangled part area was small, and the coefficient of variation of EC/V was small, resulting in a woven fabric with little variation.

[Comparative Example 1]
Except for changing the ionic surfactant adhesion rate to 70 ppm in the oiling step, the same procedure as in Example 1 was carried out. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in Table 3 below. The woven fabric had a large water drop contact angle and a large coefficient of variation of EC/V, resulting in a large variation.

[Comparative Example 2]
Except for changing the ionic surfactant adhesion rate to 840 ppm in the oiling step, the same procedure as in Example 1 was carried out. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in Table 3 below. The water drop contact angle was small, and the coefficient of variation of EC/V was large, resulting in a woven fabric with variation.

[Comparative Example 3]
The same procedure as in Example 1 was carried out except that in the winding process, the short-period oscillation width ratio B was set to 0.2 and the package width W was set to 8.5 cm. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in Table 3 below. The coefficient of variation of the unentangled part area was large, and the coefficient of variation of EC/V was large, resulting in a woven fabric with variation.

[Comparative Example 4]
The same procedure as in Example 1 was carried out except that the package width W in the winding process was set to 32 cm. The physical properties of the obtained polyamide 66 fiber and the evaluation results of the woven fabric are shown in Table 3 below. The coefficient of variation of the unentangled part area was large, and the coefficient of variation of EC/V was also large, resulting in a woven fabric with variation.

The synthetic fiber for airbags of the present invention has excellent water inclusion (instantaneous hydrophilicity of the yarn) in weaving using WJL, which dramatically improves weft yarn flight properties (ability to follow sprayed water), and has a uniform non-entangled area, which gives it excellent uniform and linear flight properties (uniform yarn flight properties). These two characteristics make it possible to weave at high speeds without variation in quality across the width of the base fabric. Therefore, the synthetic fiber for airbags of the present invention can be suitably used as a weaving yarn, particularly a weft yarn, for weaving airbag fabrics.

1 Package 2 Paper tube 3 Spin head 4 Spinneret 5 Cold air chamber 6 Oil supply device (finishing agent application device)
Reference Signs List 7 Take-up roller 8 First roller 9 Second roller 10 Third roller 11 Fourth roller 12 Yarn path control guide 13 Intertwining device 14 Winding machine 15 Single yarn 16 Water drop W Width of winding package B Short period oscillation width ratio θ Twirl angle at start of winding α Water drop contact angle a Length of non-entangled portion b Width of non-entangled portion

Claims (16)

A synthetic multifilament fiber for airbags having entangled and unentangled portions, characterized in that the water droplet contact angle on the surface of the single yarn is 50 to 75°, and the variation in the area of unentangled portions per 20 cm is 10% or less in CV value. 2. The synthetic fiber for airbags according to claim 1, wherein the area of the unentangled portions is in the range of 12.5 to 20 ^cm2 when evaluated every 20 cm in the length direction of the fiber. A synthetic fiber for airbags as described in claim 1 or 2, having a single yarn count of 60 to 250. A synthetic fiber for airbags according to claim 1 or 2, having a single yarn fineness of 1 to 7 dtex. A synthetic fiber for airbags according to claim 1 or 2, having a single yarn count of 200 to 250 and a single yarn fineness of 1.0 dtex to 1.8 dtex. A synthetic fiber for airbags as described in claim 1 or 2, having a degree of entanglement of 10 to 35 pieces/m. A synthetic fiber for airbags as described in claim 1 or 2, in which the variation in the length direction of the water droplet contact angle on the surface of a single yarn is 5% or less in CV value. A synthetic fiber for airbags as described in claim 1 or 2, in which the finishing agent adhesion rate is 0.6 to 1.2 weight %. The synthetic fiber for airbags according to claim 1 or 2, in which an anionic surfactant containing a phosphorus atom and/or an anionic surfactant containing a sulfur atom is attached in an amount of 200 to 500 ppm based on the fiber weight. The following requirements (1) to (4):
(1) The total fineness is 150 to 800 dtex;
(2) Tenacity is 7.5 to 9 cN/dtex;
(3) Elongation is 15 to 25%; and (4) Boiled water shrinkage is 4 to 11%;
3. The synthetic fiber for an airbag according to claim 1 or 2, which satisfies the above. A winding package of synthetic fiber for airbags as described in claim 1 or 2, wherein the width W of the package is 8 to 22 cm. The following steps:
A step of winding synthetic fibers spun by melt spinning onto a tube using a winding machine equipped with a traverser for swinging the yarn in the tube axial direction, the yarn passing through one or more finishing agent applying (oiling) devices, multi-stage drawing rollers, an entanglement applying device, and one or more yarn path regulating guides provided before and after the entanglement applying device;
wherein in said step, the tension before winding is 0.1 to 0.3 cN, and the short-period oscillation width ratio B in the oscillation of the yarn by a traverser is 0.5 to 5%. A method for producing synthetic fibers for airbags as described in claim 12, wherein the width W of the package obtained by winding the synthetic fibers around a tube is 8 to 22 cm. The method for producing synthetic fibers for airbags according to claim 12 or 13, wherein the finishing agent is applied by the finishing agent application device so that the anionic surfactant containing phosphorus atoms and/or the anionic surfactant containing sulfur atoms adheres to the fiber in an amount of 200 to 500 ppm based on the fiber weight. The method for producing a synthetic fiber for an airbag according to claim 12 or 13, wherein the finishing agent application device is provided at two or more positions different from each other in the yarn path direction, and the oil supply portions of at least two of the finishing agent application devices face each other. The following steps:
weaving a fabric in a water jet loom at a weaving speed of 800 rpm or more using the synthetic fiber for an airbag according to claim 1 or 2 as a weft;
A method for producing a fabric for an airbag, comprising:

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