KR20110109116A - Polyester fiber for airbag and preparation method thereof - Google Patents

Abstract

The present invention relates to a polyester yarn that can be used in the fabric for airbags, in particular, 400 to 650 denier fineness, 15% or more cut elongation, 1.2% or more dry heat shrinkage, the cut elongation (S ¹ ) and dry heat shrinkage rate A polyester yarn for airbags having a sum of (S ² ) of 18% to 25%, and a method for manufacturing the same, and a fabric for airbags produced therefrom.
The polyester yarn of the present invention has excellent initial mechanical properties with low initial modulus and thus provides excellent air barrier effect with excellent storage properties and shape stability when used as an airbag fabric, and at the same time minimizes the impact on the passengers. Can be protected safely.

Description

Polyester yarn for air bag and manufacturing method thereof {POLYESTER FIBER FOR AIRBAG AND PREPARATION METHOD THEREOF}

The present invention relates to a polyester yarn usable in an airbag fabric, and more particularly, to a polyester yarn of high strength and low modulus having excellent mechanical properties, flexibility, shape stability, and the like, and a manufacturing method thereof, and an airbag fabric using the same. It is about.

In general, an air bag detects a collision shock applied to a vehicle at a speed of about 40 km / h or more at a speed of about 40 km / h, and then explodes a gunpowder to gas into the airbag cushion. By supplying and expanding, it refers to a device that protects the driver and passengers.

Items required for airbag fabrics include low breathability for smooth deployment in the event of a crash, high strength to prevent damage and rupture of the airbag itself, high heat resistance, and flexibility to reduce impact on passengers.

In particular, the airbags used in automobiles are manufactured in a certain form, and then folded in order to minimize the volume of the airbags. Allow it to expand and deploy.

Therefore, in order to effectively maintain the folding and packageability of the airbag when installing the vehicle, to prevent damage and rupture of the airbag itself, to exhibit excellent airbag cushion deployment performance, and to minimize the impact on passengers, the airbag fabric has excellent mechanical properties. In addition, foldability and flexibility to reduce the impact on passengers is very important. However, airbag fabrics that maintain excellent air blocking effect and flexibility at the same time for the safety of the passengers, sufficiently endure the impact of airbags and can be effectively mounted in a vehicle have not been proposed.

Conventionally, polyamide fibers such as nylon 66 have been used as a material for yarn for airbags. However, nylon 66 is excellent in impact resistance, but inferior in terms of moisture resistance, light resistance, shape stability and high raw material cost compared to polyester fiber.

On the other hand, Japanese Patent Application Laid-Open No. 04-214437 proposes the use of polyester fibers in which such defects are alleviated. However, in the case of manufacturing air bags using conventional polyester yarns, it is difficult to store them in a narrow space when mounted in a vehicle due to high stiffness, and excessive heat shrinkage occurs at high temperature heat treatment due to high elasticity and low elongation. In addition, there have been limitations in maintaining sufficient mechanical properties and development performance under the harsh conditions of high temperature and high humidity.

Therefore, the fiber yarn maintains excellent mechanical properties and air blocking effect, suitable for use as a vehicle airbag fabric, and maintains excellent mechanical properties under the harsh conditions of flexibility, storage properties, and high temperature and high humidity to reduce the impact on passengers. Research on development is needed.

The present invention is to provide a polyester yarn for airbags to ensure excellent mechanical properties, flexibility, shape stability to be used in the fabric for airbags, and to maintain sufficient performance under the harsh conditions of high temperature and high humidity.

The present invention also provides a method for producing the polyester yarn.

The present invention also provides a fabric for an air bag manufactured using the polyester yarn.

In the present invention, the fineness is 400 to 650 denier, the elongation at break is 15% or more and the dry heat shrinkage is at least 1.2%, and the sum of the cut elongation (S ¹ ) and the dry heat shrinkage (S ² ) is as shown in the following formula 1. Provided are polyester yarns for airbags.

[Calculation 1]

18 ≤ S ¹ + S ² ≤ 25

In the above formula,

S ¹ is the breaking elongation of the polyester yarn (%),

S ² is the dry heat shrinkage (%) of a polyester yarn.

The present invention also comprises the step of melt spinning a polymer containing at least 70 mol% polyethylene terephthalate and an intrinsic viscosity of 1.2 to 1.8 dl / g at 270 to 305 ℃ to prepare a polyester non-drawn yarn, and the polyester non-drawn yarn It provides a method of producing a polyester yarn for the airbag comprising the step of stretching.

The present invention also provides a fabric for an air bag manufactured using the polyester yarn.

Hereinafter, a polyester yarn for an airbag according to a specific embodiment of the present invention, a manufacturing method thereof, and an airbag fabric prepared therefrom will be described in more detail. However, this is presented as an example of the invention, whereby the scope of the invention is not limited, it is apparent to those skilled in the art that various modifications to the embodiments are possible within the scope of the invention.

In addition, unless otherwise indicated throughout the specification, "including" or "containing" refers to the inclusion of any component (or component) without particular limitation and refers to the addition of another component (or component). It cannot be interpreted as excluding.

The fabric for polyester airbag is melt spun to a polymer containing polyethylene terephthalate (hereinafter referred to as "PET") to produce an unstretched yarn, and after drawing it to obtain a stretched yarn, the polyester yarn obtained through this process is It can be produced by weaving. Therefore, the properties of the polyester yarn is directly or indirectly reflected in the physical properties of the fabric for the polyester airbag.

However, in order to apply polyester as an airbag yarn instead of polyamide fibers such as conventional nylon 66, the high temperature and high humidity stiffness due to the low folding heat and low melting heat capacity due to the high modulus and stiffness of the polyester yarn Under the conditions, it should be possible to overcome the deterioration of physical properties and consequently the deterioration of development performance.

Since polyester has a lower shrinkage rate than nylon, when heat treatment is performed during fabric manufacturing, air bag fabric is not airtight, and it is difficult to provide excellent air blocking effect and has a rigid molecular chain. In this case, the packing is significantly reduced. In addition, the carboxyl end groups (hereinafter referred to as "CEG") in the polyester molecular chain attack the ester group under high temperature and high humidity conditions to cause molecular chain breakage, thereby deteriorating physical properties after aging. Becomes

Accordingly, the present invention by optimizing the range of physical properties such as fineness, elongation, shrinkage, initial modulus, etc. in polyester yarn to an excellent degree, excellent mechanical properties and air barrier such as toughness and tear strength while significantly lowering the stiffness It can maintain the performance and can be effectively applied to airbag fabric.

In particular, as a result of the experiments of the present inventors, by manufacturing the fabric for the airbag from a polyester yarn having a predetermined characteristic, it shows more improved folding properties, form stability, and air blocking effect, when used as a fabric for airbags, better storage performance in the vehicle mounting, etc. It has been found that even under the harsh conditions of packing and high temperature and high humidity, excellent mechanical properties, air leakage prevention, airtightness and the like can be maintained.

In accordance with one embodiment of the present invention, the present invention provides a polyester yarn having a predetermined characteristic. The polyester yarn has a fineness of 400 to 650 denier, an elongation at break of 15% or more and a dry heat shrinkage rate of 1.2% or more, and the sum of the cutting elongation (S ¹ ) and the dry heat shrinkage rate (S ² ) is represented by the following Equation 1. May be as

[Calculation 1]

18 ≤ S ¹ + S ² ≤ 25

In the above formula,

S ¹ is the breaking elongation of the polyester yarn (%),

S ² is the dry heat shrinkage (%) of a polyester yarn.

It is preferable that such polyester yarn contains polyethylene terephthalate (PET) as a main component. At this time, the PET can be added to the various additives in the manufacturing step, in order to exhibit a suitable physical properties for the fabric for the air bag may be a yarn containing at least 70 mol% or more, more preferably 90 mol% or more. have. Hereinafter, the term PET means a case where the PET polymer is 70 mol% or more without any special explanation.

Polyester yarn according to an embodiment of the invention is prepared under melt spinning and stretching conditions described below, the fineness is 400 to 650 denier, the elongation at break is 15% or more, the dry heat shrinkage is 1.2% or more, As shown, the sum of the elongation at break (S ¹ ) and the dry heat shrinkage rate (S ² ) is 18% to 25%.

In general, polyester has a structure of higher stiffness than nylon due to its molecular structure, and thus exhibits low elongation, high shrinkage, and toughness and toughness to absorb and endure high-temperature gas energy when used as an airbag fabric. Mechanical properties such as strength are significantly reduced. In addition, when using a fabric made from such a polyester yarn as a fabric for the air bag has a disadvantage of poor folding and packing (packing) when mounted on the vehicle due to the characteristics of high modulus (high modulus). By the way, the polyester yarn obtained through the controlled melt spinning and stretching process exhibits properties of high strength low modulus and exhibits better mechanical properties than previously known polyester industrial yarns. In particular, the polyester yarn of the present invention has a characteristic that the elongation is minimized with low initial modulus, so that the cut elongation and dry heat shrinkage are optimized.

That is, the polyester yarn has an elongation at break of at least 15% or 15% to 23%, preferably at least 16.5% or 16.5% to 21%, and a dry heat shrinkage of at least 1.2% or 1.2% to 6.5%, more preferably. May be at least 15% or from 1.5% to 5.7%. In addition, the sum of the cutting elongation (S ¹ ) and dry heat shrinkage (S ² ) of the yarn may be 18% to 25%, preferably 20% to 24%, as shown in the above formula 1. Due to such low stretching characteristics, the airbag fabric manufactured from the polyester yarn may solve the high stiffness problem of the conventional PET fabric, and may exhibit excellent folding property, flexibility, and storage property.

In the present invention, in order to effectively absorb the impact energy generated instantaneously during the operation of the airbag by controlling the cutting elongation and dry heat shrinkage of the yarn in the optimum range at the same time can improve the mechanical properties and folding properties of the final fabric. High strength and high elongation is required to have excellent stiffness and tear strength along with excellent toughness and tear strength so that the fabric can safely absorb the instantaneous impact energy of the exhaust gas generated by the explosives inside the airbag at the same time. Low dry heat shrinkage is required. At this time, the cutting elongation and dry heat shrinkage of the yarn in the present invention needs to satisfy the above range.

In particular, the elongation at break of the yarn is represented by S ¹ in the formula 1, that is, by the case of the extensometer, whose value remains above 15%, it is possible to secure the high toughness low initial modulus (Young's Modulus) with (toughness) . As a result, when applied to the fabric for the airbag, not only the gas energy of high temperature and high pressure can be sufficiently absorbed, but also excellent folding property can be secured to give excellent storage and development properties when the vehicle is mounted. In addition to the cutting elongation of the yarn, the present invention maintains the yarn dry heat shrinkage represented by S ² in the formula 1 above 1.2%, due to the yarn shaking due to the high relaxation rate or high temperature of the roller in actual weaving process It can prevent the trimming and improve sacrifice. At the same time, the cutting elongation and dry heat shrinkage ratio of the yarn is preferably at least 18% in terms of toughness and storage property when applied to an airbag fabric as shown in Equation 1, and is 25% or less. It is preferable to become a radioactive yarn and a yarn in terms of yarn for airbags.

In addition, in order for the polyester yarn of the present invention to be effectively used for fabrics for airbags, it is necessary to maintain low fineness and high strength in terms of cushioning performance and absorption performance capable of absorbing high-pressure deployment energy during airbag deployment. Possible total fineness of the yarn can be 400 to 650 denier. The yarn preferably has a fineness of 400 denier or more in terms of energy absorption performance, and preferably has a fineness of 650 denier or less in terms of ensuring excellent folding of the airbag cushion.

Polyester yarn according to an embodiment of the present invention has a modulus (M ¹ ) of 60 to 100 g / dee at 1% elongation measured at room temperature by the method of ASTM D 885, modulus (M ² at elongation 2%) ) Is 20 to 60 g / de, and the ratio (M ¹ / M ² ) of the modulus may be as shown in Equation 2 below.

[Equation 2]

1.7 ≤ M ¹ / M ² ≤ 3.5

In the above formula,

M ¹ is the modulus of polyester yarn (g / de) at 1% elongation measured at room temperature,

M ² is the modulus (g / de) of polyester yarn at 2% elongation measured at room temperature.

As described above, the polyester yarn of the present invention can increase the mechanical properties and folding properties of the final fabric by adjusting the elongation curve of the yarn to the optimum range. In particular, the polyester yarn exhibits properties of high strength low modulus and may exhibit a lower modulus (Young's modulus) than previously known polyester industrial yarns. That is, the yarn may have a modulus (M ¹ ) at 1% elongation of 60 to 100 g / de, preferably 75 to 95 g / de, and a modulus (M ² ) at 2% elongation of 20 to 60 g / de, preferably 22 to 55 g / de. As a conventional general industrial yarn, the polyester yarn has a modulus of more than 110 g / de at 1% elongation and 80% of modulus at 2% elongation. Compared to g / de or more, the polyester yarns of the present invention can be those having a significantly lower modulus.

In addition, the initial modulus for the polyester yarn of the present invention has a ratio (M ¹ / M ² ) of modulus (M ¹ ) at elongation 1% and modulus (M 2) at elongation 2% as shown in Equation 2 above 1.7. To 3.5, preferably 1.9 to 3.3. When the yarn is applied to the airbag fabric, the fabric can safely absorb the instantaneous impact energy of the exhaust gas generated by the explosive explosion inside the airbag, and at the same time, have excellent airtightness and folding property so that effective development can be achieved. It is necessary to meet the modulus range against specific elongation conditions with low initial modulus as described above.

In this case, the modulus of the polyester yarn is a physical property value of the elastic modulus obtained from the slope of the elastic section of the stress-strain diagram obtained in the tensile test, and when the object is stretched from both sides, the elastic modulus indicating the degree of stretching and deformation of the object The value corresponds to If the modulus of the fiber is high, the elasticity is good, but the stiffness of the fabric may be poor. If the modulus is too low, the stiffness of the fabric may be good, but the elastic recovery force may be lowered, resulting in poor mechanical properties such as the toughness of the fabric. As such, airbag fabrics made from polyester yarns that optimize initial modulus to a lower range than conventional ones solve the high stiffness problem of conventional polyester fabrics, and have excellent folding, flexibility, and storage properties. Together it can exhibit excellent mechanical properties.

In particular, the modulus of yarn at 1% elongation of M ¹ in the formula 2 is preferably at least 60 g / de in terms of crystal structure and orientation required for physical property expression as an airbag yarn, and in terms of foldability of an airbag cushion 100 g / de or less is preferable. In the formula 2, the rapid deployment performance aspects of the modulus of air bag deployment when the air bag cushion of the yarn in 2% elongation as a M ² 20 g / de or more are preferred, and a 60 g / de or less preferably in the folding property side of the air bag cushion Do. Furthermore, the elongation modulus at 1% ratio of the modulus (M ²⁾ of the (M ¹⁾ and the elongation ^{2% (M 1 / M 2} ) is at least 1.7 in the deployment performance aspects of the physical properties of the expression, and the air bag cushion of yarn for air bags It is preferable to keep it, and it is preferable to keep it at 3.5 or less in terms of the folding property of the fabric for airbags.

At the same time, the polyester yarn has an improved intrinsic viscosity, i.e., at least 0.8 dl / g or 0.8 to 1.2 dl / g, preferably at least 0.85 dl / g or 0.85 to 1.15 dl / as compared to previously known polyester yarns. g, more preferably 0.9 dl / g or more, or an intrinsic viscosity of 0.9 to 1.1 dl / g. Intrinsic viscosity is preferably secured in the above range in order to prevent thermal deformation in the coating process, etc. when the polyester yarn is applied to the air bag.

The intrinsic viscosity of the yarn should be 0.8 dl / g or more to exert high strength at low stretching to satisfy the required strength of the airbag yarn, and otherwise it may be forced to express physical properties with high stretching. When the high stretching is applied, the orientation of the fiber is increased to show high modulus physical properties, and thus it is difficult to achieve excellent folding properties of the fabric. Therefore, it is preferable to maintain the intrinsic viscosity of the yarn at 0.8 dl / g or more to enable low modulus expression by applying a low stretching. In addition, the yarn viscosity is 1.2 dl / g or more because the stretching tension at the time of stretching may cause problems in the process, 1.2 dl / g or less is more preferred. In particular, the polyester yarn of the present invention maintains such a high degree of intrinsic viscosity, while providing low ductility with low stretching, and at the same time can provide sufficient mechanical properties, impact resistance, toughness, etc. to the fabric for the airbag Higher strength characteristics can be further imparted.

Therefore, it is possible to manufacture a fabric for an airbag which simultaneously exhibits excellent mechanical properties and storage properties, form stability, impact resistance, and air barrier effect by using a polyester yarn exhibiting such low initial modulus and high elongation, preferably high intrinsic viscosity. Become. Therefore, by using the polyester yarn, it is possible to obtain a fabric for an air bag, which exhibits lower ductility and folding property, flexibility, and storage property, but also exhibits excellent impact resistance, shape stability, mechanical properties, and airtightness. These polyester fabrics for airbags exhibit excellent mechanical properties, shape stability, and air barrier effects, while providing excellent folding properties and storage properties when mounted in tight spaces of cars, while minimizing the impact on passengers with excellent flexibility. Since it can protect, it can be preferably applied as a fabric for airbags.

In addition, the polyester yarn of the present invention is prepared under the melt spinning and stretching conditions described below, the carboxyl end group (CEG) content significantly lower than the previously known polyester yarn, that is, 50 meq / kg or less, preferably It may exhibit a CEG content of 40 meq / kg or less, more preferably 30 meq / kg or less. The carboxyl end groups (CEG) in the polyester molecular chains attack the ester bonds at high temperature and high humidity to cause molecular chain cleavage, thereby degrading physical properties after aging. Particularly, if the CEG content exceeds 50 meq / kg, the ester bond is cleaved by the CEG under high humidity conditions when the air bag is used for application, so that the physical property is degraded, so the CEG content is preferably 50 meq / kg or less. Do.

On the other hand, polyester yarn according to an embodiment of the present invention may exhibit a tensile strength of 8.8 g / d to 10.0 g / d, preferably 9.2 g / d to 9.8 g / d. In addition, the polyester yarn may exhibit a toughness (Toughness) of the yarn defined by the following formula 3 70 to 95 J / ㎥. As described above, by securing the intrinsic viscosity, initial modulus, and elongation range in an optimum range, the polyester yarn of the present invention can not only secure strength and physical properties to an excellent degree, but also exhibit excellent performance when manufactured as an airbag fabric. Can be.

[Calculation 3]

In the formula 3,

F represents the load applied when the length of the polyester yarn or fabric is increased by dl,

dl represents the lengthened length of the polyester yarn or fabric.

The polyester yarn has a higher level of toughness (breakage) than conventional polyester yarns, thereby effectively absorbing and withstanding the energy of hot-high pressure gas. In particular, as the toughness of polyester yarn for airbags shows 70 J / m 3 to 95 J / m 3, preferably 75 J / m 3 to 90 J / m 3, it can effectively absorb and withstand the energy of hot-high pressure gas. It can be used very effectively as a yarn for airbags.

In this case, the toughness is energy consumed until the fiber (including the yarn or the fabric; the same below) is broken by the tensile force, as represented by Equation 3, and means the resistance of the fiber to a sudden impact. If a fiber increases its length from l to l + dl at a load F, then the work is F · dl, so the toughness required to cut the fiber is as shown in Equation 1 above. That is, the toughness represents the cross-sectional area of the yarn and the fabric's strength-elongation curve (see FIG. 2), and the higher the strength and elongation of the yarn used in the fabric, the higher the toughness expressed in the fabric. In particular, when the toughness of the fabric for the airbag is lowered, the resistance of the fabric capable of sufficiently absorbing the instantaneous deployment impact of the inflator having a high temperature-high pressure during airbag deployment becomes low, resulting in the fabric of the airbag being easily torn. Therefore, when the toughness of the polyester yarn for airbag in the present invention, for example, less than 70 kJ / ㎥ may be difficult to use in the fabric for the airbag.

The polyester yarn preferably has a shrinkage stress of 0.005 to 0.075 g / d at 150 ° C. corresponding to a laminate coating temperature of a general coating fabric, and a shrinkage stress at 200 ° C. corresponding to a sol coating temperature of a general coating fabric. It is preferred that it is from 0.005 to 0.075 g / d. That is, the shrinkage stress at 150 ° C. and 200 ° C. should be 0.005 g / d or more, respectively, to prevent sagging of the fabric due to heat during the coating process, and should be 0.075 g / d or less to be cooled at room temperature after the coating process. Relaxation stress can be alleviated. The shrinkage stress is based on values measured under a fixed load of 0.10 g / d.

In order to prevent deformation in the heat treatment process such as coating as described above, the polyester yarn is also 40% to 55% crystallinity, preferably 41% to 52%, more preferably 41% to 50% Can be. The degree of crystallinity of the yarn should be more than 40% to maintain thermal morphological stability when applied to the fabric for airbags, and when the crystallinity exceeds 55%, there is a problem that the impact absorption performance is deteriorated because the amorphous region is reduced It is preferable to become 55% or less.

In addition, the polyester yarn may be a single yarn fineness of 2.5 to 6.8 DPF, preferably 2.92 to 4.55 DPF. In order for the yarn to be effectively used in fabric for airbags, the total fineness of the yarn is applicable since the cushioning performance and the absorption performance of absorbing high-pressure deployment energy during airbag deployment must be maintained at low fineness and high strength. It may be 400 to 650 denier. The more filaments of the yarn may give a soft touch, but if too many may not have good radioactivity, the number of filaments may be 96 to 160.

On the other hand, the polyester yarn according to an embodiment of the invention as described above may be produced by melt spinning PET to prepare a non-stretched yarn, a method of stretching the unstretched yarn, as described above, Specific conditions or processing methods may be directly or indirectly reflected on the physical properties of the polyester yarn, thereby producing a polyester yarn having the above-described physical properties.

In particular, through the process optimization as described above, the elongation at break is at least 15% and the dry heat shrinkage is at least 1.2%, and the sum of the cutting elongation (S ¹ ) and the dry heat shrinkage (S ² ) is 18% to 1 as shown in the above formula 1. It has been found that a 25% polyester yarn for airbags can be obtained. In addition, the optimization of the melt spinning and stretching process in the present invention, it is possible to minimize the carboxyl end group (CEG, Carboxyl End Group) which is present as an acid under high humidity conditions to cause the basic molecular chain cleavage of polyester yarn It turns out that. Therefore, such a polyester yarn exhibits a low initial modulus and a high elongation range at the same time, and thus can be preferably applied to fabrics for airbags having excellent mechanical properties and storage properties, shape stability, impact resistance, and air blocking effect.

When explaining the polyester yarn manufacturing method in more detail for each step as follows.

The method of manufacturing a polyester yarn for air bags comprises the steps of melt spinning a polymer containing at least 70 mol% polyethylene terephthalate and an intrinsic viscosity of 1.2 to 1.8 dl / g at 270 ℃ to 305 ℃ to prepare a polyester unstretched yarn, And stretching the polyester unstretched yarn.

First, with reference to the accompanying drawings, it can be briefly described an embodiment of the melt spinning and stretching process of the present invention to be easily carried out by those skilled in the art.

1 is a process diagram schematically showing a polyester yarn manufacturing process including the melt spinning and stretching step according to an embodiment of the present invention. As shown in FIG. 1, the method of manufacturing the polyester yarn for an air bag of the present invention melts the polyester chip manufactured in the manner described above, and cools the molten polymer spun through the detention with quenching-air. The emulsion is applied to the undrawn yarn using an emulsion roll (or oil-jet, 120), and the emulsion applied to the undrawn yarn is subjected to a constant air pressure using a pre-interlacer (130). It can be uniformly dispersed on the surface. Then, after the stretching process through the multi-stretching apparatus (141 ~ 146), and finally by interlacing the yarn at a constant pressure in the second collector (2 ^nd Interlacer, 150) (winding in the winding machine 160) Can be produced to produce yarn.

On the other hand, in the production method of the present invention, first, a polyester unstretched yarn is manufactured by melt spinning a high viscosity polymer including polyethylene terephthalate.

In this case, in order to obtain a polyester non-drawn yarn satisfying a low initial modulus and a high elongation range, the melt spinning process is preferably performed at a low temperature range to minimize thermal decomposition of the PET polymer. In particular, low-temperature spinning, for example, 270 to 305 ° C. to minimize the degradation of physical properties according to the process with respect to the intrinsic viscosity and CEG content of the high viscosity PET polymer, that is, to maintain the high viscosity and low CEG content of the PET polymer , Preferably from 280 to 300 ° C, more preferably from 282 to 298 ° C. Here, the spinning temperature refers to the extruder temperature, and when the melt spinning process is performed above 305 ° C., thermal decomposition of the PET polymer occurs in a large amount, thereby decreasing molecular weight and increasing CEG content due to a decrease in intrinsic viscosity. It is not preferable because it can be large, and the surface damage of the yarn may lead to a decrease in overall physical properties. In contrast, when the melt spinning process is performed at less than 270 ° C., the melting of the PET polymer may be difficult, and the spinning may be poor due to N / Z surface cooling, and thus, the melt spinning process may be performed within the above temperature range. .

As a result of the melt spinning process of PET in this low temperature range, the decomposition reaction of PET is minimized to maintain a high intrinsic viscosity to ensure high molecular weight, so that a high stretching ratio is not applied in a subsequent stretching process. It was found that a strong yarn can be obtained, and thus, a low-stretching process can be performed to effectively lower the modulus, thereby obtaining a polyester yarn meeting the above-described physical properties.

In addition, the melt spinning process may be carried out at a lower spinning tension in terms of minimizing the PET polymer decomposition reaction, i.e., to minimize spinning tension, for example, a rate of melt spinning the PET by 300 m / It can be adjusted at a low speed of min to 1,000 m / min, preferably from 350 to 700 m / min. As such, as the melt spinning process of PET is selectively performed under low spinning tension and low spinning speed, the decomposition reaction of PET may be further minimized.

On the other hand, the unstretched yarn obtained through such a melt spinning process is at least 0.8 dl / g or 0.8 dl / g to 1.2 dl / g, preferably at least 0.85 dl / g or 0.85 dl / g to 1.15 dl / g, more preferably May represent an intrinsic viscosity of 0.9 dl / g or more or 0.9 dl / g to 1.1 dl / g. In addition, the CEG content in the molecule of the unstretched yarn obtained through low-temperature spinning may be 50 meq / kg or less, preferably 40 meq / kg or less, and more preferably 30 meq / kg or less. The intramolecular CEG content of these untwisted yarns can be maintained at the same level in the stretched yarn, that is, the polyester yarn, which has undergone the subsequent stretching process.

In particular, as described above, in order to manufacture a high strength low modulus polyester yarn, melt spinning and stretching using a high-viscosity PET polymer, for example, a PET polymer having an intrinsic viscosity of 1.2 dl / g or more in a non-drawn yarn manufacturing process It is desirable to effectively lower the modulus by maintaining the high viscosity range through the process to exhibit high strength with low stretching. However, the intrinsic viscosity is more preferably 1.8 dl / g or less in order to prevent the molecular chain cleavage and the pressure increase due to the discharge amount in the spinning pack due to the rise of the melting temperature of the PET polymer.

On the other hand, in order to maintain the excellent physical properties even under high temperature and high humidity conditions when the polyester yarn is applied to the fabric for airbags, the intramolecular CEG content of the PET polymer is preferably 30 meq / kg or less. Here, the CEG content of the PET polymer is maintained in the range as low as possible even after the melt spinning and stretching process, the final produced polyester yarn exhibits excellent physical properties under high strength and excellent morphological stability, mechanical properties, harsh conditions It is desirable to be able to secure. In this aspect, if the CEG content of the PET chip exceeds 30 meq / kg, the intramolecular CEG content of the polyester yarn finally produced through melt spinning and stretching processes is excessive, such as 30 meq / kg to 50 meq / Increasing to more than kg, the ester bond is cleaved by the CEG under high humidity conditions may cause a decrease in the properties of the yarn itself and the fabric produced therefrom.

In particular, such high viscosity and low CEG content PET polymers are melt-spun under low temperature conditions as described above to minimize thermal decomposition of PET polymers, thereby minimizing the difference in intrinsic viscosity and CEG content between PET polymer and polyester yarn. can do. For example, the difference in intrinsic viscosity between a PET polymer and a polyester yarn is melt spun to be 0.5 dl / g or less or 0 to 0.5 dl / g, preferably 0.4 dl / g or 0.1 to 0.4 dl / g The process can be carried out. In addition, the difference in the intramolecular CEG content between the PET polymer and the polyester yarn is 20 meq / kg or less or 0 to 20 meq / kg, preferably 15 meq / kg or less or 3 to 15 meq / kg to perform the process Can be.

The present invention by suppressing the decrease in the intrinsic viscosity of the PET polymer and the increase in the content of CEG as possible, while maintaining excellent mechanical properties of the polyester yarn at the same time, it can secure excellent elongation, and a high-strength low modulus yarn suitable for airbag fabric It can manufacture.

In addition, the PET chip is preferably spun through a mold designed to have a fineness of the monofilament is 2.5 DPF to 6.8 DPF. That is, the denier of the monofilament should be 2.5 DPF or more in order to reduce the possibility of the trimming due to the occurrence of the trimming during the spinning and the interference during cooling, and the fineness of the monofilament should be 6.8 DPF or less in order to increase the cooling efficiency. .

In addition, after melt spinning the PET, a non-drawn PET yarn may be manufactured by adding a cooling process. It is preferable to proceed with this cooling process by the method of adding the cooling wind of 15-60 degreeC, and it is preferable to adjust the cooling air quantity to 0.4-1.5 m / s in each cooling wind temperature conditions. As a result, the PET non-drawn yarn showing various physical properties according to an embodiment of the present invention can be produced more easily.

On the other hand, after producing the polyester non-drawn yarn through this spinning step, the non-drawn yarn is drawn to prepare a drawn yarn. In this case, the stretching process may be performed under a total draw ratio of 5.0 to 6.5, preferably 5.0 to 6.0. The polyester non-drawn yarn is optimized to melt spinning process to maintain a high intrinsic viscosity and low initial modulus and to minimize the intramolecular CEG content. Therefore, when the drawing process is carried out under high draw ratio conditions in excess of 6.5, it may be over-stretched level, so that cutting or wool may occur in the drawn yarn, and the yarn of low elongation high modulus is produced by high degree of fiber orientation. Can be. In particular, when the elongation of the yarn is lowered and the modulus is increased under such high draw ratio conditions, the folding and storage properties may be poor when applied as an airbag fabric. On the other hand, when the drawing process is performed under a relatively low draw ratio, the fiber orientation is low, and the strength of the polyester yarn manufactured therefrom may be partially lowered. However, when the stretching process is performed under a stretching ratio of 5.0 or more in terms of physical properties, for example, a high strength low modulus polyester yarn suitable for application to an airbag fabric, etc. can be manufactured, and thus, the stretching process may have a stretching ratio of 5.0 to 6.5. It is preferable to proceed under conditions.

According to another suitable embodiment of the present invention, melt spinning is carried out using a high viscosity polyethylene terephthalate polymerized chip to produce a low modulus polyester yarn while simultaneously satisfying the properties of high strength and low shrinkage in a direct spinning drawing process It may include a process of drawing, heat setting, relaxing, winding through a multi-stage high-speed roller to wind up the winder.

The stretching process may be performed after passing the undrawn yarn through a roller roller under the condition of 0.2% to 2.0% of oil pick-up amount.

In the relaxation process, the relaxation rate is preferably 1% to 14%, and when it is less than 1%, it is difficult to express the shrinkage rate, and it may be difficult to manufacture high elongation low modulus fibers as high fiber orientation is formed, as in the high draw ratio conditions. If it exceeds 14%, the noise on the high-pressure roller becomes severe and workability cannot be secured.

In addition, the stretching process may further perform a heat-setting process for heat-treating the undrawn yarn at a temperature of approximately 170 to 250 ℃, preferably 175 to 240 ℃, more preferably for the proper progress of the stretching process May be heat treated at a temperature of 180 to 245 ° C. Here, if the temperature is less than 170 ℃ thermal effect is not enough to reduce the relaxation efficiency is difficult to achieve the shrinkage rate, if it exceeds 250 ℃, the yarn strength due to thermal decomposition and the generation of tar on the rollers increases to increase workability Can be.

At this time, the winding speed may be performed at 2,000 to 4,000 m / min, preferably 2,500 to 3,700 m / min.

In accordance with another embodiment of the present invention, there is provided a polyester fabric for an air bag comprising the polyester yarn described above.

In the present invention, the airbag fabric refers to a woven fabric or a nonwoven fabric used for manufacturing an airbag for an automobile, and is characterized by being manufactured using a polyester yarn manufactured through the process as described above.

In particular, the present invention by using a polyester fiber having a high-strength low modulus rather than a polyester fiber having a high strength-low elongation and a high modulus, not only the energy absorption capacity at the time of inflating the air bag, but also excellent It is possible to provide a polyester fabric for airbags having morphological stability, air barrier properties, and excellent folding, flexibility and storage properties. In addition, the airbag fabric is not only excellent in room temperature physical properties, but also maintains excellent mechanical properties and airtightness after aging (aging) under severe conditions of high temperature and high humidity.

More specifically, the airbag fabric of the present invention is a tensile strength of 220 to 350 kgf / inch measured at room temperature by the American Society for Testing and Materials Standard ASTM D 5034 method, preferably in the range of 230 to 300 kgf / inch Can be. In the case of the tensile strength, it is preferable to be 220 kgf / inch or more in terms of properties of existing airbags, and in reality, it is preferable to be 350 kgf / inch or less in terms of physical properties.

The fabric for the air bag is 20% to 60% cutting elongation measured at room temperature by the American Society for Testing and Materials Standard ASTM D 5034 method, preferably 30% to 50% range. In the case of the cut elongation, it is preferable to be 20% or more in terms of properties of existing airbags, and in reality, it is preferable to be 60% or less in terms of physical properties.

The polyester fabric for the airbag may be a toughness (Toughness) of the fabric, which is defined by Formula 3 below, 3.5 to 6.0 kJ / ㎥.

[Calculation 3]

In the formula 3,

F represents the load applied when the length of the polyester yarn or fabric is increased by dl,

dl represents the lengthened length of the polyester yarn or fabric.

The polyester fabric has a higher level of toughness (fracture) than the conventional polyester fabric, thereby effectively absorbing and withstanding the energy of high-temperature gas. In particular, the toughness of the polyester fabric for airbags is 3.5 kJ / ㎥ to 6.0 kJ / ㎥, preferably 3.8 kJ / ㎥ to 5.7 kJ / ㎥, it can effectively absorb and withstand the energy of high-temperature gas It can be used very effectively as yarn and fabric for airbags. Lowering the toughness of the fabric for the airbag lowers the resistance of the fabric that can sufficiently absorb the instantaneous deployment impact of the inflator having high temperature and high pressure during airbag deployment, resulting in the tearing of the fabric for the airbag easily. Therefore, when the toughness of the fabric in the present invention, for example, less than 3.5 kJ / ㎥ may be difficult to apply to the fabric for the air bag.

In addition, the airbag fabric is required to have an excellent tear strength level because it is rapidly inflated by high-temperature gas, the tear strength indicating the burst strength of the fabric for airbags is the American Material Testing Association standard for uncoated fabrics When measured by the ASTM D 2261 TONGUE method can be 18 to 30 kgf, the tear strength of the coating fabric can be 30 to 60 kgf, measured by the American Society for Testing and Materials Standard ASTM D 2261 TONGUE method. Here, if the tear strength of the fabric for the airbag is less than the lower limit, i.e., 18 kgf and 30 kgf, respectively, in each of the uncoated fabric and the coated fabric, the airbag bursts when the airbag is deployed, which may cause a great risk to the airbag function. It may be. On the other hand, when the tear strength of the airbag fabric exceeds the upper limit, that is, 30 kgf and 60 kgf, respectively, in the uncoated fabric and the coated fabric, the edge comb resistance of the fabric is lowered and the airbag is deployed. It may be undesirable because the air barrier property deteriorates sharply.

Fabric for airbag according to the present invention, the fabric shrinkage rate in the warp direction and weft direction of each measured by the method of ASTM D 1776 may be 1.0% or less, preferably 0.8% or less, respectively, after the aging and inclined direction and weft The far-end shrinkage in the direction may be 1.0% or less, preferably 0.8% or less. Here, in terms of the shape stability of the fabric, it is most preferable that the fabric shrinkage ratio in the warp direction and the weft direction do not exceed 1.0%.

As described above, the airbag fabric may maintain a toughness and tear strength of the fabric by using a polyester yarn having a high strength and low modulus, and may significantly lower the stiffness of the fabric. The fabric for the air bag has a stiffness of 1.5 kgf or less or 0.3 to 1.5 kgf, preferably 1.2 kgf or less, or 0.3 to 1.2 kgf, more preferably 0.8 kgf or less, or 0.3 to 0.3, according to the American Society for Testing and Materials, ASTM D 4032. 0.8 kgf. As such, the stiffness of the fabric is significantly lowered than that of the conventional polyester fabric. Thus, the fabric for the airbag of the present invention may exhibit excellent folding and flexibility, and improved storage performance when the airbag is mounted. As such, the stiffness of the fabric is significantly lowered than that of the conventional polyester fabric. Thus, the fabric for the airbag of the present invention may exhibit excellent folding and flexibility, and improved storage performance when the airbag is mounted.

In order to use the fabric of the present invention, it is preferable to maintain the above-mentioned stiffness range, and if the stiffness is too low, it may not have sufficient protective support function when the airbag is inflated and deployed. This may degrade the storage. In addition, in order to prevent the storage property from deteriorating due to becoming too hard and being difficult to fold, the stiffness is preferably 1.5 kgf or less, particularly when less than 460 denier, and preferably 0.8 kgf or less, even when 550 denier or more. It is good to become the following.

Static air permeability according to the American Material Testing Association standard ASTM D 737 method of the fabric for the air bag is 10.0 cfm or less or 0.3 to 10.0 cfm, preferably 8.0 cfm or less or 0.3 when △ P is 125 pa for the uncoated fabric To cpm, more preferably 5.0 cfm or less, or 0.3 to 5.0 cfm, and when ΔP is 500 pa, 14 cfm or less or 4 to 14 cfm, preferably 12 cfm or less, or 4 to 12 cfm. Can be. In addition, the dynamic air permeability according to the American Society for Testing and Materials Standard ASTM D 6476 method is 1,700 mm / s or less, preferably 1,600 mm / s or 200 to 1,600 mm / s, more preferably 1,400 mm / s or 400 To 1,400 mm / s. In this case, the static air permeability refers to the amount of air that penetrates into the fabric when a certain pressure is applied to the fabric for the air bag, and the smaller the denier per filament of the yarn and the higher the density of the fabric, the lower the value. In addition, the dynamic air permeability refers to the degree of air permeation to the fabric when the average instantaneous differential pressure of 30 to 70 kPa is applied. May have

In particular, the air permeability of the fabric for the airbag can be significantly lowered by including the rubber component coating layer in the fabric, it is possible to ensure the air permeability of the value close to almost 0 cfm. However, when the rubber component coating is performed as described above, the airbag coating fabric of the present invention has a static air permeability of 0.1 cfm or less from 0 to 0.1 cfm when △ P is 125 pa according to the American Society for Testing and Materials Standard ASTM D 737 method. It may be preferably 0.05 cfm or less or 0 to 0.05 cfm, and when ΔP is 500 pa, 0.3 cfm or less or 0 to 0.3 cfm, preferably 0.1 cfm or less or 0 to 0.1 cfm.

Here, the fabric for the airbag of the present invention is to maintain the airtightness of the fabric for the airbag when the uncoated fabric and the coated fabric, respectively, exceeds the upper limit of the static air permeability range, or exceeds the upper limit of the dynamic air permeability range. In terms of aspect, this may not be desirable.

In addition, according to another embodiment of the present invention, there is provided a method for producing an airbag fabric using a polyester yarn. The fabric manufacturing method for the airbag of the present invention includes the steps of weaving the dough for the airbag using the polyester yarn, refining the dough for the woven airbag, and the step of tentering the refined fabric.

In the present invention, the polyester yarn may be produced as a final airbag fabric through a conventional weaving method, refining and tentering process. At this time, the woven form of the fabric is not limited to a specific form, both the plain type and OPW (One Piece Woven) type of woven form is preferred.

In particular, the fabric for the airbag according to the present invention can be produced through a beaming, weaving, refining, and tenterizing process using the polyester yarn as a weft and warp yarn. The fabric can be produced using a conventional weaving machine, and is not limited to using any particular loom. However, plain weave fabrics can be manufactured using Rapier Loom, Air Jet Loom or Water Jet Loom, and OPW fabrics are Jacquard loom. Loom).

In addition, the airbag fabric of the present invention preferably further comprises a coating layer consisting of at least one of a silicone resin, polyvinyl chloride resin, polyethylene resin, polyurethane resin, or the like coated or laminated on the surface, the kind of coating resin It is not limited only to the above-mentioned materials. The resin coating layer may be applied by the knife coating method, the doctor blade method, or the spray coating method, but this is also not limited to the above-mentioned method.

The coating amount per unit area of the resin coating layer may be used to 20 to 200 g / m ² , preferably 20 to 100 g / m ² . Particularly, in the case of OPW (One Piece Woven) type side curtain airbag fabric, the coating amount is preferably 30 g / m ² to 95 g / m ² , and in the case of plain weave fabric for air bag, the coating amount is 20 g / m ² to 50 g / m ² levels are preferred.

The coated airbag fabric is manufactured in the form of an airbag cushion having a predetermined shape while undergoing cutting and sewing. The airbag is not limited to a particular form and may be manufactured in a general form.

On the other hand, according to another embodiment of the present invention, there is provided an airbag system including the above airbag. The airbag system can be equipped with conventional devices well known to those skilled in the art. The airbag may be largely classified into a frontal airbag and a side curtain airbag. The frontal airbag includes a driver's seat, a passenger seat, a side protection, a knee protection, ankle protection, a pedestrian protection airbag, and the side curtain type airbag protects passengers in a vehicle collision or rollover accident. Accordingly, the airbag of the present invention includes both a frontal airbag and a side curtain airbag.

In the present invention, matters other than those described above can be added or subtracted as required, and therefore, the present invention is not particularly limited thereto.

According to the present invention, there is provided a polyester yarn for airbags having excellent mechanical properties such as toughness and tear strength while significantly lowering the stiffness and fabric for airbags manufactured using the same.

These polyester yarns for airbags are optimized for high strength, high elongation, low shrinkage, and low initial modulus, which not only provides excellent morphological stability, mechanical properties, and air barrier effect when used as fabrics for airbags, but also at the same time excellent folding properties. And it is possible to secure the flexibility to significantly improve the storage when mounting the car and at the same time can minimize the impact on the passengers to protect the occupants safe.

Therefore, the polyester yarn of the present invention and the polyester fabric using the same can be very preferably used for manufacturing a vehicle airbag.

1 is a process diagram schematically showing a polyester yarn manufacturing process for an airbag according to an embodiment of the present invention.
Figure 2 shows an example of the strength-elongation curve of a typical fiber, the area of this strength-elongation curve can be defined as toughness (breaking days, J / ㎥).
Figure 3 shows the strength-elongation curves of polyester yarn according to Example 1 of the present invention.
Figure 4 shows the strength-elongation curves of polyester yarn according to Comparative Example 1 of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the following examples.

Example  1-5

After preparing a polyester non-drawn yarn by melt spinning and cooling a PET polymer having a predetermined intrinsic viscosity and CEG content, the non-drawn yarn was stretched at a predetermined draw ratio and subjected to heat treatment to prepare a polyester yarn. At this time, the intrinsic viscosity of the PET polymer and the intramolecular CEG content, spinning rate and spinning tension during the melt spinning process, dissipation temperature conditions, elongation ratio, heat treatment temperature are as shown in Table 1 below, the rest of the conditions for the production of polyester yarn The usual conditions were followed.

division Example 1 Example 2 Example 3 Example 4 Example 5 PET content (mol%) 100 100 100 100 100 Intrinsic viscosity of PET chip (dl / g) 1.25 1.33 1.40 1.50 1.60 CEG of PET chip (meq / kg) 30 27 24 23 22 Spinning temperature (℃) 293 295 295 295 295 Total draw ratio 5.99 6.03 6.07 6.11 6.15 Heat treatment temperature (℃) 235 239 243 240 244 % Relaxation 5.6 5.7 5.8 6.1 6.3

Physical properties of the polyester yarns prepared according to Examples 1 to 5 were measured by the following methods, and the measured physical properties are summarized in Table 2 below.

1) Tensile strength and Elongation at break

Tensile strength and elongation at break of polyester yarn were measured using a universal testing machine (Instron), the sample length was 250 mm, the tensile speed was set to 300 mm / min, the initial load was set to 0.05 g / d.

In addition, the elongation value (%) corresponding to each tensile strength (1.0 g / d, 5.0 g / d, 8.8 g / d) is confirmed from the tensile strength and elongation curve according to the elongation. The strength (g / d) and maximum elongation (%) at the point of strength were confirmed.

2) dry heat shrinkage

Dry heat shrinkage was measured for 2 minutes at a temperature of 180 ° C. and an ultra-tension (30 g) using Testrite MK-V equipment from Testrite, UK.

3) Young's modulus

Young's modulus and elongation were measured by the method of ASTM D 885, and the modulus at elongation 1% and 2%, ie, at 1% and 2% elongation, is shown in Table 2 below. It was.

4) Toughness of Yarn

The toughness (Toughness, J / m 3) value of the yarn was calculated by the following Equation 3.

[Calculation 3]

In the formula 3,

F represents the load applied when the length of the polyester yarn or fabric is increased by dl,

dl represents the lengthened length of the polyester yarn or fabric.

5) Crystallinity

The density ρ of the polyester yarn was measured at 25 ° C. according to the density gradient pipe method using n-heptane and carbon tetrachloride, and the crystallinity was calculated according to the following equation (4).

[Calculation 4]

Where ρ is the density of the yarn, ρ _c is the density of the crystal (1.457 g / cm ^{3 for} PET), and ρ _a is the density of the amorphous (1.336 g / cm ^{3 for} PET).

6) intrinsic viscosity

Extract the emulsion from the sample using carbon tetrachloride, melt with OCP (Ortho Chloro Phenol) at 160 ± 2 ℃, and measure the sample viscosity in the viscosity tube using an automatic viscosity meter (Skyvis-4000) at 25 ℃. To obtain the intrinsic viscosity (IV) of the polyester yarn in accordance with the following formula (5).

[Calculation 5]

Intrinsic Viscosity (IV) = {(0.0242 × Rel) +0.2634} × F

Where

이고,

ego,

이다.

to be.

7) CEG Content

Carboxyl End Groups (CEGs) of polyester yarns are prepared by placing 0.2 g of a sample into a 50 mL Erlenmeyer flask, adding 20 mL of benzyl alcohol, according to the requirements of ASTM D 664 and D 4094. plate) up to 180 ℃, hold for 5 minutes to completely dissolve the sample, and then cooled to 160 ℃, 5-6 drops of phenolphthalene when reaching 135 ℃, titrated with 0.02N KOH, colorless to pink The CEG content (COOH million equiv./kg of sample) was calculated by the following Equation 6 at the titration point.

[Calculation 6]

CEG = (A-B) × 20 × 1 / W

Where A is the amount of KOH consumed in the titration of the sample (mL), B is the amount of KOH consumed in the titration of the blank sample (mL), and W is the weight of the sample (g).

8) single yarn fineness

Single yarn fineness was measured by taking the yarn by 9000 m and measuring its total fineness (Denier) by dividing the number of filaments.

division Example 1 Example 2 Example 3 Example 4 Example 5 Crystallinity (%) 43.2 43.9 45.2 45.6 46.3 Intrinsic Viscosity of Yarn (dl / g) 0.93 0.97 1.05 1.11 1.20 CEG of yarn (meq / kg) 33 29 27 26 26 Tensile Strength of Yarn (g / d) 9.1 9.2 9.25 9.3 9.35 Cutting Elongation of Yarn (S ¹ ,%) 16.5 17 18.7 19.0 18.5 Dry heat shrinkage rate of yarn (S ² ,%) 5.2 5.3 2.8 4.0 5.3 S ¹ + S ² (%) 21.7 22.3 21.5 23.0 23.8 Modulus of yarn
(At 1% elongation, M ¹ , g / de) 85 84 79 78 82 Modulus of yarn
(At elongation 2%, M ² , g / de) 47.0 46.6 26.8 26.3 26.0 M ¹ / M ² 1.81 1.80 2.95 2.97 3.15 Toughness of yarn
(Toughness, J / ㎥) 79 80 86 87 86 Single yarn fineness (DPF) of yarn 3.82 3.23 2.92 4.61 4.17 Total fineness of yarn (de) 420 420 420 600 600 Number of filaments of yarn 110 130 144 130 144

Comparative example  1-5

A polyester yarn of Comparative Examples 1 to 5 was prepared according to the same method as Examples 1 to 5 except for the conditions described in Table 3 below.

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 PET content (mol%) 100 100 100 100 100 Intrinsic viscosity of PET chip (dl / g) 0.85 0.90 0.95 0.90 0.95 CEG of PET chip (meq / kg) 50 47 43 47 43 Spinning temperature (℃) 301 302 305 302 305 Total draw ratio 4.95 5.03 5.10 5.03 5.10 Heat treatment temperature (℃) 220 223 227 223 227 % Relaxation 4.7 4.75 4.8 4.75 4.8

Physical properties of the polyester yarn prepared according to Comparative Examples 1 to 5 are summarized in Table 4 below.

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Crystallinity (%) 41.7 41.9 41.9 41.9 41.9 Intrinsic Viscosity of Yarn (dl / g) 0.61 0.63 0.65 0.63 0.65 CEG of yarn (meq / kg) 57 53 50 53 50 Tensile Strength of Yarn (g / d) 6.9 7.2 7.5 7.2 7.5 Cutting Elongation of Yarn (S ¹ ,%) 10 11 13 11 13 Dry heat shrinkage rate of yarn (S ² ,%) 15.5 15 13.7 15 13.7 S ¹ + S ² (%) 25.5 26 26.7 26 26.7 Modulus of yarn
(At 1% elongation, M ¹ , g / de) 115 119 125 119 125 Modulus of yarn
(At elongation 2%, M ² , g / de) 85 91 93 91 93 M ¹ / M ² 1.35 1.31 1.34 1.31 1.34 Toughness of yarn
(Toughness, J / ㎥) 59 63 67 63 67 Single yarn fineness (DPF) of yarn 7.35 6.94 6.94 10.0 9.14 Total fineness of yarn (de) 500 500 500 680 680 Number of filaments of yarn 68 72 72 68 72

In addition, the strength-elongation curves of the polyester yarns according to Example 1 and Comparative Example 1 are shown in FIGS. 3 and 4, respectively.

As shown in FIG. 3, the yarn for the airbag according to Example 1 exhibits high strength in the strength-elongation graph, that is, the highest tensile strength of 9.1 g / d. It can be seen that. Therefore, the polyester yarn according to Example 1 has excellent characteristics of high strength, high elongation and low modulus, and thus, excellent mechanical properties and air barrier effect can be secured when applied to a vehicle airbag fabric.

On the other hand, as shown in Figure 4, the airbag yarn according to Comparative Example 1, the highest strength when cutting in the strength-elongation graph is only 6.9 g / d, the initial slope of the graph also appears large and shows a high initial modulus It can be seen. It can be seen that it shows low toughness and high modulus. As described above, the polyester yarn according to Comparative Example 1 exhibits low toughness and high initial modulus, thereby decreasing the ability to absorb high-pressure high-pressure inflator gas energy when applied as an airbag fabric, and airbag cushion airtightness. The packaging performance is also worse, which makes it unsuitable for use as a fabric for airbags.

Manufacturing example  1-5

Weaving fabrics for airbags through a rapier weaving machine using polyester yarns prepared according to Examples 1 to 5, manufacturing fabrics for airbags through refining and tentering processes, and liquid silicone rubber (LSR) on the fabrics. ) Was coated by a knife over (knife over ro1l coating) method to prepare a silicone coated fabric.

At this time, the inclination and weft density of the fabric, weaving form, the resin coating amount is as shown in Table 5, the remaining conditions were in accordance with the conventional conditions for the manufacture of polyester fabric for airbags.

division Example 1 Example 2 Example 3 Example 4 Example 5 Weaving Density (Inclined X Weft) 49 x 49 49 x 49 49 x 49 43 x 43 43 x 43 Weaving type (plain weave / opw) Plain weave Plain weave Plain weave Plain weave Plain weave Heat treatment / vulcanization temperature (℃) 180 185 190 185 190 Rubber ingredient 180 185 190 185 190 Resin Coating Amount (g / m ² ) Liquid silicone Liquid silicone Liquid silicone Liquid silicone Liquid silicone

Physical properties of the polyester fabric for each air bag manufactured using the polyester yarn prepared according to Examples 1 to 5 were measured by the following method, and the measured physical properties are summarized in Table 6 below.

(a) Toughness of the fabric

Toughness (J / m 3) values were calculated by the following equation (3).

[Calculation 3]

In the formula 3,

F represents the load applied when the length of the polyester yarn or fabric is increased by dl,

dl represents the lengthened length of the polyester yarn or fabric.

At this time, the toughness of the fabric was measured with an uncoated fabric before coating treatment.

(b) tear strength

After the uncoated fabric before coating and the coated fabric after coating, each specimen was cut 75 mm x 200 mm in width, and then each of the upper and lower portions of the specimen was subjected to ASTM D 2261 TONGUE. Located between the left and right spaces of the jaw face at the top and bottom of the device, the jaw face spacing is based on 76 mm / min, uncoated fabric and coated fabric at a speed of 300 mm / min The tear strength of was measured, respectively.

(c) tensile strength and cutting elongation

Cut the specimen with uncoated fabric before coating and fix it to the lower clamp of the tensile strength measuring device according to ASTM D 5034, the strength and elongation at the time of breaking the airbag fabric specimen while moving the upper clamp upward. Was measured.

(d) Fabric shrinkage in warp and weft directions

Fabric shrinkage in the warp / weft direction was measured according to the American Society for Testing and Materials, ASTM D 1776. First, after cutting the specimen with an uncoated fabric before coating treatment, mark the length before shrinking in the warp and weft directions by 20 cm, and measure the contracted length of the specimen heat-treated in the chamber at 149 ° C. for 1 hour in the warp direction. And weaving shrinkage ratio {(length before contraction-length after contraction) / length before contraction x 100%} in the weft direction.

(e) lecture

The uncoated fabric before coating treatment was measured by the circular bend method using a ductility measuring apparatus according to the American Society for Testing and Materials Standard ASTM D 4032. In addition, the cantilever method may be applied as a method of measuring the stiffness, and the stiffness can be measured by measuring the bend length of the fabric using a cantilever measuring device, which is a test bench that is inclined at an angle to give a bend to the fabric.

(f) after

The thickness of the uncoated fabric before coating treatment was measured according to the American Society for Testing and Materials, ASTM D 1777.

(g) air permeability

After allowed to stand over one day under the American Society for Testing and Materials specification according to ASTM D 737 20 ℃ the uncoated fabric before coating, 65% RH, △ P, each 125 of the pressure pa and 500 pa of the air is 38 cm ² The amount passing through the circular section was measured and expressed as static air permeability.

In addition, it was shown by measuring the dynamic air permeability of the uncoated fabric using a dynamic air permeability tester (TEXTEST FX 3350 Dynamic Air Permeability Tester) according to ASTM D 6476.

division Example 1 Example 2 Example 3 Example 4 Example 5 Fabric toughness
(Toughness, kJ / ㎥) 3.75 3.83 3.92 5.4 5.6 Tear Strength (kgf) / Uncoated of Fabric 19 19 20 26 26 Tear Strength (kgf) / Coating of Fabric 36 37 38 38 40 Tensile strength of fabric (kgf / inch) 227 230 234 297 305 Elongation at break of fabric (%) 37 37 39 38 40 Fabric Shrinkage
(%) slope 0.5 0.5 0.4 0.4 0.5 Weft 0.3 0.3 0.4 0.3 0.3 Lecture degree (kgf) 0.40 0.40 0.35 1.00 0.90 Thickness (mm) 294 294 295 338 338 Static air permeability
(cfm) △ P = 125 pa 1.0 0.9 0.8 0.6 0.6 △ P = 500 pa 9.5 9.3 9.2 5.4 5.4 Dynamic Air Permeability (mm / s) 620 610 590 450 430

compare Manufacturing example  1-5

Except for using the polyester yarn of Comparative Examples 1 to 5 instead of the polyester yarn prepared according to Examples 1 to 5 according to the same method as Preparation Examples 1 to 5 poly for airbags of Comparative Preparation Examples 1 to 5 An ester fabric was prepared, and the physical properties thereof were summarized in Table 7 below.

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Fabric toughness
(Toughness, kJ / ㎥) 2.5 2.7 2.9 2.7 2.9 Tear Strength (kgf) / Uncoated of Fabric 13 14 15 19 20 Tear Strength (kgf) / Coating of Fabric 21 23 23 23 24 Tensile strength of fabric (kgf / inch) 187 195 200 195 200 Elongation at break of fabric (%) 20 21 22 20 22 Fabric Shrinkage
(%) slope 1.3 1.3 1.2 1.2 1.1 Weft 1.2 1.0 0.9 1.0 0.9 Lecture degree (kgf) 2.1 1.9 1.8 2.3 2.3 Thickness (mm) 303 305 305 350 350 Static air permeability
(cfm) △ P = 125 pa 2.4 2.3 2.2 2.2 2.1 △ P = 500 pa 13.5 13.3 13.0 12.6 12.5 Dynamic Air Permeability (mm / s) 1,900 1,850 1,800 1,950 1,850

As shown in Table 6, fabrics for airbags of Preparation Examples 1 to 5 using a polyester yarn prepared from Examples 1 to 5 and optimized for cutting elongation and dry heat shrinkage ratio are 3.75 to 5.6 kJ / m ³ , Tear strength of uncoated fabric is 19 to 26 kgf, tensile strength is 227 to 305 kgf / inch, and fabric shrinkage is 0.4% to 0.5% and 0.3% to 0.4% in the warp and weft directions respectively. It can be seen that having. At the same time, it can be seen that the polyester fabrics for airbags of Preparation Examples 1 to 5 have an excellent optimum range of 0.35 to 1.0 kgf, and thus have excellent foldability and storage properties along with excellent morphological stability and mechanical properties. . In particular, the airbag fabrics of Preparation Examples 1 to 5 using a yarn of high strength, high elongation and low shrinkage rate, the static air permeability (△ P = 125 pa) of the non-coated fabric is 0.6 to 1.0 cfm level, static air permeability (△ It can be seen that P = 500 pa) is in the range of 5.4 to 9.5 cfm, resulting in excellent airtightness results.

On the other hand, as shown in Table 7, the fabric for airbags of Comparative Preparation Examples 1 to 5 using the polyester yarns of Comparative Examples 1 to 5 has a shrinkage of 0.9% to 1.3% in the warp direction and the weft direction, and the tensile strength Is 187 to 200 kgf / inch, it can be seen that the tear strength of the uncoated fabric is significantly dropped to 13 to 20 kgf. As such, when a fabric having significantly lower mechanical properties such as tensile strength and tear strength is used in the airbag device, problems may occur due to a decrease in mechanical properties such as an airbag bursting when the airbag is deployed.

Static air permeability (△ P = 125 pa) of the uncoated fabric according to Comparative Production Examples 1 to 5 is 2.1 to 2.4 cfm level, static air permeability (△ P = 500 pa) is significantly increased to 12.5 to 13.5 cfm level. It can be seen that the airtightness is reduced, if the air permeability is increased in this way, the air can be easily released during deployment of the air bag may not be able to act as an air bag.

Claims (11)

The fineness is 400 to 650 denier, the elongation at break is 15% or more, the dry heat shrinkage is 1.2% or more, and the sum of the cut elongation (S ¹ ) and dry heat shrinkage (S ² ) is as shown in the following formula 1 poly Ester yarn:
[Calculation 1]
18 ≤ S ¹ + S ² ≤ 25
In the above formula,
S ¹ is the breaking elongation of the polyester yarn (%),
S ² is the dry heat shrinkage (%) of polyester yarn. The method of claim 1,
Modulus (M ¹ ) at elongation 1% measured at room temperature by the method of ASTM D 885 is 60 to 100 g / de, modulus (M ² ) at elongation 2% is 20 to 60 g / de, and the modulus Polyester yarns for airbags whose ratio (M ¹ / M ² ) is shown in Formula 2:
[Calculation 2]
1.7 ≤ M ¹ / M ² ≤ 3.5
In the above formula,
M ¹ is the modulus of polyester yarn (g / de) at 1% elongation measured at room temperature,
M ² is the modulus of polyester yarn (g / de) at 2% elongation measured at room temperature. The method of claim 1,
A polyester yarn for airbags having a single yarn fineness of 2.5 to 6.8 DPF and a yarn filament applied of 96 to 160 strands. The method of claim 1,
Polyester yarns for airbags made from polyester chips having an intrinsic viscosity of 1.2 to 1.8 dl / g. Preparing a polyester non-stretched yarn by melt spinning a polymer containing 70 mol% or more of polyethylene terephthalate and having an intrinsic viscosity of 1.2 to 1.8 dl / g at 270 to 305 ° C., and
Drawing the polyester undrawn yarn
A method for producing a polyester yarn for airbags according to any one of claims 1 to 4, including. The method of claim 5,
Process for producing a polyester yarn for airbags to perform the stretching process to the total draw ratio of 5.0 to 6.5. The method of claim 5
After stretching the undrawn yarn, a method for producing a polyester yarn for airbags further comprising a heat setting step at a temperature of 170 to 250 ℃. The method of claim 5
A method for producing a polyester yarn for airbags, further comprising a relaxation process of 1% to 14% relaxation rate after stretching the unstretched yarn. A polyester fabric for an airbag comprising the polyester yarn according to any one of claims 1 to 4. 10. The method of claim 9,
Polyester fabric for air bags with a ductility of 1.5 kgf or less according to ASTM D 4032 method. 10. The method of claim 9,
Polyester fabric for air bags with a tear strength of 18 kgf or more, measured by the American Society for Testing and Materials, ASTM D 2261 TONGUE.

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