JPH08134717A - Production of polyester fiber for air bag - Google Patents

Abstract

PURPOSE: To obtain a high-grade polyester fiber having mechanical properties such as tensile strength and elongation necessary for an air bag base fabric when woven or knitted and capable of giving fabrics with flexibility as well as such mechanical properties. CONSTITUTION: Polyethylene terephthalate 0.8-1.1 in intrinsic viscosity is subjected to melt spinning at a delivery linear velocity of 4-10m/min and passed through a heating zone at >=300 deg.C with a length of 5-10cm placed under a spinneret followed by cooling, and the resultant filament yarn is sucked and bundled by a suction device set up within 1.5m under the spinneret, and the tension difference between the outlet of the suction device and the inlet of a take-up roller is set at <=0.001g/d, and the filament yarn is taken up by the take-up roller revolving at a velocity of 400-600m/min and then drawn at a draw ratio 0.8-0.9 times the breaking draw ratio, thus obtaining the objective polyester fiber for air bag with a single fiber fineness of <=1.5 denier, tenacity of >=8g/d, and breaking elongation of >=14%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyester fiber for an air bag, which is capable of obtaining an air bag base fabric which is excellent in mechanical properties such as strength and elongation and is flexible and easy to store. .

[0002]

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

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

However, the base fabric obtained by coating the synthetic fiber woven fabric with rubbers can improve heat resistance and airtightness by coating with rubbers, but the base fabric becomes hard and the storability deteriorates. There's a problem.

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

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

Japanese Unexamined Patent Publication (Kokai) No. 3-167312 describes a method for obtaining a polyester fiber for an airbag, which has high toughness, impact resistance, and excellent durability. The fiber has improved knot strength. As a result, an airbag base fabric having improved impact resistance as compared with the conventional one can be obtained, and the flatness of the base fabric is also improved.

However, in this method, in order to make the resulting fiber resistant to impact and excellent in durability,
It is necessary to increase the single yarn fineness, and if the fibers obtained by this method are woven at a high density in order to increase airtightness, the fabric will be inferior in flexibility and only airbags with poor storability can be obtained. was there.

Therefore, it has sufficient strength and durability,
Moreover, it is not easy to produce a polyester fiber such that the obtained fabric has excellent flexibility, and a method for producing a polyester fiber capable of obtaining a flexible airbag base fabric having such excellent mechanical properties at the same time. Has not yet been established.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides an airbag base fabric having the mechanical characteristics and flexibility required for an airbag base fabric at the same time. It is a technical object to provide a method for producing a polyester fiber for use.

[0011]

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

That is, the present invention has an intrinsic viscosity of 0.8 to 1.
The polyethylene terephthalate of 1 was melt spun at a discharge linear velocity of 4 to 10 m / min, and the length provided directly under the die was 5 to 10
After passing through a heating zone with a temperature of 300 cm or more and 300 ℃ or more, after cooling, suction is focused by a suction device installed within 1.5 m from the die, and the tension difference between the suction device outlet and the take-in roller inlet is 0.
001 g / d or less, it is taken up by a take-up roller having a speed of 400 to 600 m / min, and then drawn at 80 to 90% of the breaking draw ratio, and the single yarn fineness is 1.5 d or less and the strength is 8 g / d or more,
The gist is a method for producing a polyester fiber for an air bag, which is characterized in that a fiber having an elongation of 14% or more is obtained.

The present invention will be described in detail below.

The polyester fiber in the present invention is substantially composed of polyethylene terephthalate (PET), and the intrinsic viscosity is a value measured at 20 ° C. by using an equal weight mixed solvent of phenol and tetrachloroethane. .
Must be 8 to 1.1. If the intrinsic viscosity is lower than 0.8, the fiber will be inferior in strength and durability, and if it is higher than 1.1, the spinning stress will be high and it will be difficult to suppress the orientation.

Further, the PET may contain a third component such as a heat-resistant agent, a flame retardant, a matting agent, etc. within a range that does not impair the original properties of the polyester.

In the present invention, PET having such an intrinsic viscosity is melt-spun, the spun yarn is passed through a heating zone, cooled, suction-focused and taken up, and then hot-stretched. , Single yarn fineness of 1.5 d or less, strength of 8 g / d or more,
Elongation is a method for producing a polyester fiber for an airbag of 14% or more, and a feature of the present invention is that a fiber having a small single yarn fineness is drawn as an undrawn yarn before the orientation of molecules advances, and hot drawing is performed. By applying it, it is to make a fiber with high strength.

Specifically, when producing a multifilament having a small single yarn fineness that can impart flexibility to the obtained fabric, the orientation of the single yarn tends to advance in the spinning process due to the effect of the tension applied to the single yarn. Therefore, even if it is subjected to hot drawing, it is difficult to obtain a high-strength fiber.

The tension applied to the running fiber is almost proportional to the change in the speed from spinning to take-up and the resistance of air applied to the fiber.

Therefore, in order to reduce the change in speed from spinning to drawing, a suction device is installed between the spinneret and the take-up roller at a position where the fiber has cooled to some extent, and suction is performed in the running direction of the fiber. This accelerates the running speed of the fiber to reduce the difference from the take-up speed, and as a result, reduces the tension applied to the fiber and delays the progress of the orientation of the undrawn yarn.

Further, a multifilament having a small single yarn fineness is also susceptible to air resistance, and the air resistance applied to the fiber increases as the focusing position moves away from the spinneret, the tension applied to the single yarn increases, and the orientation advances. Because there is a tendency
In the present invention, a suction device is installed within 1.5 m below the mouthpiece, and the suction device simultaneously suctions and bundles the fibers.

Generally, in order to uniformly spun multifilaments having a small single yarn fineness, it is preferable to increase the discharge speed and make the cooling start point close to the spinneret. However, in the present invention, in order to suppress the orientation, immediately after spinning. It is necessary to sufficiently heat the fibers.

Therefore, melt spinning is carried out at a discharge linear velocity of 4 to 10 m / min, and the fiber is passed through a heating zone having a length of 5 to 10 cm and a temperature of 300.degree.

When the discharge linear velocity is less than 4 m / min, the draft ratio represented by the ratio between the take-up speed and the discharge linear velocity becomes too large and the orientation proceeds, and when it is higher than 10 m / min,
Since the time for passing through the heating zone is short and the heating is not sufficient, the effect of suppressing the orientation becomes small.

In the present invention, a fiber having a single yarn fineness of 1.5 d or less is produced. Therefore, a spinning nozzle having a hole diameter of 0.15 to 0.35 mm is used and the polymer is discharged at a single hole discharge rate of 0.1 to 1.0 g / min. It is preferable.

Regarding the heating zone, when the length of the heating zone is less than 5 cm or the temperature is less than 300 ° C., the fibers are not sufficiently heated and the orientation cannot be suppressed.

The temperature of the heating zone is not particularly limited as long as it is 300 ° C. or higher, but preferably 300 to
It is 450 ℃. The temperature in the heating zone is too high or the length is too long.
If the length exceeds 10 cm, the fibers are overheated to become fibers with a lot of yarn unevenness, or yarn breakage occurs, and the operability tends to deteriorate.

The heating method in the heating zone is not particularly limited as long as the temperature can be kept uniform, and a cylindrical heating element is arranged around the fiber or a heating gas is used. Examples include a method of spraying the fibers.

Next, the fibers that have passed through the heating zone are cooled. At this time, it is preferable to blow cooling air from the outer circumference of the fibers toward the center in order to cool the fibers uniformly. After cooling the fiber, the fiber is sucked and focused at the same time by a suction device installed within 1.5 m below the die, and the difference in tension applied to the fiber between the suction device outlet and the take-up roller inlet is 0.001 g / d. Below.

If the difference in tension is more than 0.001 g / d, the orientation of the undrawn yarn is promoted and the fiber having the desired strength cannot be obtained.

Further, this difference in tension can be arbitrarily changed by changing the suction speed of the suction device. Then, after applying the oil agent to the bundled fibers, the take-up speed
Collect at 400-600 m / min.

When the take-up speed is lower than 400 m / min, the productivity is lowered, and when the take-up speed is higher than 600 m / min, the difference in speed from spinning to take-up is large and the tension is large, so that the orientation proceeds. Therefore, it is difficult to increase the strength of the fiber even if it is subjected to hot drawing, and it is impossible to obtain the fiber having the desired strength.

Next, the drawn undrawn yarn is heat-drawn, but in order to obtain the target fiber having a strength of 8 g / d or more, it is drawn at a draw ratio of 80 to 90% of the breaking draw ratio. 8g if the draw ratio is less than 80% of the breaking draw ratio
A fiber having a strength of / d or more cannot be obtained, and if it exceeds 90%, yarn unevenness or fluff occurs, resulting in a fiber with a poor quality.

The stretching temperature is not particularly limited, but is preferably 120 to 250 ° C., more preferably
160-220 ℃, 130-250 following stretching
It is desirable that the relaxation heat treatment is performed at a temperature of 160 ° C, preferably 160 to 220 ° C.

The drawing may be carried out by a two-step method in which the film is once wound up or by a spin draw method in which spinning is carried out at a high speed, but the spin draw method is more preferable in order to improve productivity. preferable.

Further, as the method of hot stretching, it is preferable to carry out multi-stage drawing of two or more steps in order to perform with good operability, and the heating method is not particularly limited, but a heating roller, a heat plate, Using a heat box,
Examples include a method of spraying heated steam.

By the production method of the present invention as described above, it is possible to produce a polyester fiber for an air bag having a single yarn fineness of 1.5 d or less, a strength of 8 g / d or more and an elongation of 14% or more. Since the fiber has a single yarn fineness of 1.5 d or less and has such strength and elongation, it is possible to impart sufficient impact resistance and flexibility to the obtained base fabric.

[0037]

EXAMPLES The present invention will be specifically described below with reference to examples.

The method of measuring the characteristic value in the present invention is as follows.

(A) Strength and elongation Using an autograph S-100 manufactured by Shimadzu Corporation, sample length 25c
It was measured under the conditions of m and a pulling speed of 30 cm / min.

(B) Unevenness (U%) The value was measured by a half inert test using a Worcester yarn unevenness measuring device manufactured by Zellvega, Switzerland.

(C) Difference in tension The tension of the fiber at the outlet of the suction device and the inlet of the take-up roller was measured by using an electric tension meter R-3192 manufactured by Roche Shield Company of Switzerland, and the difference was obtained from the difference between the two.

Example 1, Comparative Examples 1 to 8 PET chips having an intrinsic viscosity of 0.9 were supplied to an extruder type melt spinning machine, and a spinning spinneret having 144 spinning holes with a diameter of 0.25 mm was used to spin at a spinning temperature of 305 ° C. Spinning was performed at various discharge linear velocities, and the spun fibers were passed through a heating cylinder having a length and temperature shown in Table 1 arranged immediately below the spinneret as a heating zone (Comparative Example 6 (No heating cylinder), then
Air temperature 20 ° C, air velocity 0.4 m / from a 20 cm long cylindrical cooling device
Minute cooling air was blown onto the fibers to cool them.

After cooling, a suction device was installed at the focusing position shown in Table 1 represented by the distance from the die (Comparative Example 1 did not have a suction device), the fibers were sucked and focused, and an oil agent was applied, 70
It was taken up by a heating take-off roller at ℃. Then, a pre-stretching of 1.005 times was performed between the take-up roller and the first stretching roller at 140 ° C., and then at the stretching ratio shown in Table 1 between the first stretching roller and the second stretching roller at 200 ° C. went. After that, between the second stretching roller and the heat treatment roller at 160 ℃
After 0.99 times relaxation heat treatment, wound up, 210 d / 14
4f polyester fiber was obtained.

At this time, the discharge linear velocity during melt spinning, the length of the heating zone, the temperature, the focusing position, the tension difference from the suction device outlet to the take-up roller, the take-up speed, the breaking draw ratio, the draw ratio, and the take-up speed. Is also shown in Table 1, and the single fiber fineness, strength, elongation and yarn unevenness of the obtained fiber are also shown in Table 1.

[0045]

[Table 1]

As is clear from Table 1, in Example 1, high-quality fibers having a strength of 8 g / d or more and an elongation of 14% or more and having no yarn unevenness were obtained.

On the other hand, in Comparative Example 1 in which the suction device was not used for focusing, the difference in tension applied to the fibers was large,
In Comparative Example 4, the focusing position was 2.0 m away from the spinneret, and in Comparative Example 5, the drawing speed was too fast, the orientation of the undrawn yarn proceeded, and sufficient drawing could not be performed. The obtained fiber had low strength.

In Comparative Example 2, since the draw ratio was low, the drawing could not be sufficiently performed, and the obtained fiber had low strength.

In Comparative Example 3, since the draw ratio was too high, the obtained fiber had low elongation and large yarn spots.

In Comparative Example 6, since the heating cylinder was not provided,
In Comparative Example 8, since the temperature of the heating cylinder was low, the heat treatment was insufficient, the orientation of the undrawn yarn proceeded, and the obtained fiber had low strength.

In Comparative Example 7, since the length of the heating cylinder was too long, the fiber was overheated and the obtained fiber had many yarn unevenness.

Example 2 and Comparative Example 9 Spinning was carried out using a spinneret having 144 spinning holes with a diameter of 0.3 mm, and as shown in Table 2, the discharge linear velocity at the time of melt spinning, the length of the heating zone, and the temperature. 210 d / 144 f (Example 2) and 140 d / 144 f (Comparative Example 9), except that the tension difference from the suction device outlet to the take-up roller, the take-up speed, and the draw ratio were changed. ) Polyester fiber was obtained.

Table 2 also shows the results of measuring the single yarn fineness, strength, elongation and yarn unevenness of the obtained fiber.

Example 3, Comparative Example 10 Spinning was carried out using a spinneret having 144 spinning holes with a diameter of 0.2 mm, and as shown in Table 2, the discharge linear velocity at the time of melt spinning, the length of the heating zone, and the temperature. And 140 d / 144 f (Example 3) and 210 d / 144 f (Comparative Example 10) except that the tension difference from the suction device outlet to the take-up roller, the take-up speed, and the draw ratio were changed. ) Polyester fiber was obtained.

Table 2 also shows the results of measuring the single yarn fineness, strength, elongation and yarn unevenness of the obtained fiber.

[0056]

[Table 2]

According to Examples 2 and 3, high-quality fibers having a strength of 8 g / d or more and an elongation of 14% or more and having no yarn unevenness were obtained.

On the other hand, in Comparative Example 9, since the discharge linear velocity was slow, the draft ratio became too large and the orientation proceeded, and the obtained fiber had low strength and large yarn unevenness.

In Comparative Example 10, since the discharge linear velocity was high, the heat treatment in the heating zone was insufficient and the orientation of the undrawn yarn proceeded, so that the obtained fiber had low strength and large yarn spots. .

[0060]

EFFECTS OF THE INVENTION According to the present invention, a high-quality polyester fiber which can be knitted and woven into a fabric having mechanical properties such as strength and elongation required for an airbag base fabric and flexibility. Can be manufactured.

[0061]

Front page continued (72) Inventor Naohiro Matsuo 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Ltd. Central Research Laboratory

Claims (1)

[Claims] 1. A heating zone of polyethylene terephthalate having an intrinsic viscosity of 0.8 to 1.1 melt-spun at a discharge linear velocity of 4 to 10 m / min and having a length of 5 to 10 cm and a temperature of 300 ° C. or higher provided directly under the die. After cooling and cooling, suction is focused with a suction device installed within 1.5 m from the die, and the tension difference between the suction device outlet and the take-up roller inlet is 0.001 g / d or less, and the speed is 400 to 600 m / min. An air characterized by obtaining a fiber having a single yarn fineness of 1.5 d or less, a strength of 8 g / d or more and an elongation of 14% or more by drawing it with a roller and then drawing at 80 to 90% of the breaking draw ratio. Method for producing polyester fiber for bag.