JP3130683B2 - Method for producing polyester fiber with improved dimensional stability - Google Patents

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 suitable for industrial materials, and more particularly to a polyester fiber having improved dimensional stability and suitable for rubber reinforcing applications such as tire cords and V-belts. Is a method for stably producing

[0002]

2. Description of the Related Art Polyester fibers have various excellent properties and are therefore widely used not only for clothing but also for industrial materials. In particular, polyester fibers having high strength and excellent dimensional stability are used not only for tire reinforcement but also for various industrial materials, and recently, higher performance is increasingly required. I have. For example, regarding polyester fibers for tire cords, it is required to further reduce the shrinkage in order to improve the yield during molding of the tire, and to improve ride comfort, a high modulus is required. I have. In addition, when used for large tires, improvement in fatigue resistance is required. On the other hand, polyester fibers for V-belts are required to have a high modulus in order to be maintenance-free, and in high load wrapped belt cords, high elongation, high toughness and fatigue resistant fibers are required. Has been requested.

[0003] In response to such quality requirements, polyester fibers obtained by a high-speed spinning drawing method developed and put into practical use in recent years have a low shrinkage ratio. The cord can have a high modulus while maintaining the same or lower low shrinkage.

For example, Japanese Patent Application Laid-Open No. 53-58032 proposes a method of starting from an undrawn yarn having a higher orientation than in the past and stretching the same. A tire cord using this drawn yarn is High modulus, low shrinkage, fatigue resistance, significantly improved compared to conventional polyester tire cords, excellent handling stability and ride comfort when driving at high speeds, and unevenness during tire molding (so-called Dent bulge)
Are few and are being used favorably.

Japanese Patent Application Laid-Open No. Sho 59-168119 discloses that a spinning speed of 3100 to 4000 m / min is used.
Birefringence ^{78 × 10 - 3 ~90 × 10} - 3 in the relatively highly oriented undrawn yarn was stretched to 1.67 to 1.80 times, it describes a process for producing a high-strength polyester fiber It has been shown that a polyester fiber cord using this fiber has a high modulus and low shrinkage cord close to rayon, for example, having an intermediate elongation of 3.7% and a dry heat shrinkage of 1.8%. I have.

Further, Japanese Patent Application Laid-Open No. 62-69819 discloses that a polyester is cooled and solidified by selecting a distance from a spinneret surface to a cooling air blowing surface and a cooling air blowing length within a specific range. It is described that a high-strength, low-shrinkage, and fatigue-resistant polyester fiber having both good stretchability can be obtained by performing high-speed spinning while performing multi-stage stretching of the obtained undrawn yarn.

[0007]

However, even these conventional polyester fibers have insufficient modulus and shrinkage as compared with rayon fibers and vinylon fibers having a long history. In particular, cords obtained from polyester fibers require a step of cooling after embedding and vulcanizing in rubber (so-called post cure inflation).
This cooling step has a large capital investment, and it is desirable to omit this step for cost rationalization. For this purpose, a low shrinkage equivalent to that of cords of rayon fiber and vinylon fiber is required, and the shrinkage rate of the conventional polyester fiber is still high and insufficient.

Further, as described above, when a highly oriented undrawn yarn obtained by high-speed spinning is drawn in order to obtain a polyester fiber which can be made into a high modulus, low shrinkage cord, the spinning property in the spinning process is increased. Was damaged, and single yarn breakage and yarn breakage frequently occurred, and as a result, the yarn breakage frequently occurred in the stretching step, and stable production could not be performed with good productivity.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a high-modulus, low-shrinkage polyester cord close to a rayon cord or a vinylon cord by using a polyester fiber having a high modulus. It is an object of the present invention to provide a novel method that can be manufactured stably with high productivity.

[0010]

The object of the present invention is attained by a method for producing a polyester fiber having improved dimensional stability comprising the following steps.

(A) A polyester containing ethylene terephthalate as a main repeating unit is melt-spun from a spinneret.

(B) Next, the spun yarn is blown with cooling air to be rapidly cooled, and is taken up by a take-up roll. At this time, the distance (spinning length) from the spinneret to the first take-up roll is equal to or larger than the larger one of LL1 and LL2 represented by the following formulas (1) and (2) and the following formula (3) LM or less.

LL1 = 700−0.09V (1) LL2 = 50d + 50 + H (2) LM = 1000−0.09V (3) Here, V is the spinning take-up speed (m / min), H is the distance (cm) from the spinneret surface to the cooling air blowing position, and 10 ≦ H ≦
40, and d is the single yarn denier of the undrawn yarn after the take-up.

(C) The cooled yarn is drawn at a speed of 4000 m / min or more to obtain an undrawn yarn having an intrinsic viscosity of 0.85 or more, a birefringence of 0.08 or more, and a density of 1.370 or more.

(D) The undrawn yarn is drawn 1.3 to 1.8 times to obtain a drawn yarn having a strength of 6.0 g / de or more.

The polyester fiber in the present invention is composed of a polyester containing at least 90 mol%, preferably at least 95 mol% of ethylene terephthalate repeating units in the molecular chain. Polyethylene terephthalate is suitable as such a polyester, but may contain other copolymer components of 10 mol% or less, preferably 5 mol% or less. Such copolymerization components include, for example, isophthalic acid, naphthalenedicarboxylic acid, adipic acid, oxybenzoic acid, diethylene glycol, propylene glycol,
Trimellitic acid, pentaerythritol and the like. In addition, such a polyester may contain additives such as a stabilizer and a coloring agent as needed.

The polyester of the present invention must have an intrinsic viscosity of 0.85 or more as determined from an o-chlorophenol solution at 25 ° C. When the intrinsic viscosity is less than 0.85, orientation and crystallization of the spun yarn do not easily progress, and it is difficult to obtain a polyester fiber which can be used as the high modulus and low shrinkage cord, which is the object of the present invention.

Further, in the present invention, the birefringence (Δn) of the undrawn yarn is 0.08 or more, preferably 0.09 or more, and the density (ρ) is 1.370 or more, preferably 1.70.
It needs to be 373 or more. Birefringence is 0.0
If the density is less than 8 and the density is less than 1.370, a polyester fiber which can be used as the high modulus and low shrinkage cord of the present invention cannot be obtained.

Such an undrawn polyester yarn having an intrinsic viscosity of 0.85 or more, a birefringence of 0.08 or more, and a density of 1.370 or more is slightly higher than the intrinsic viscosity of the undrawn yarn, for example, 0.95. As described above, preferably, a polyester polymer having an intrinsic viscosity of 0.95 to 1.30 is melted by a conventional method, and spun so that the denier of a single yarn after stretching is 1 to 20 de and the total denier is 500 to 2000 de. It can be obtained by discharging from a die and collecting at a take-up speed of 4000 m / min or more.

The conditions for obtaining the polyester undrawn yarn having the above intrinsic viscosity, birefringence and density include the spinning temperature, the heating conditions under the spinneret, the spinning length, etc., in addition to the intrinsic viscosity of the raw material polymer and the spinning take-off speed. They are intricately intertwined and it is quite difficult to correlate those relationships. However, in the present invention, when the following conditions are satisfied, the polyester fiber aimed at by the present invention can be stably produced even if other conditions are changed.

First, in the present invention, the spinning take-off speed needs to be 4000 m / min or more, preferably 4500 m / min or more. The birefringence and density of the undrawn yarn are
It varies somewhat depending on the spinning temperature, the heating conditions under the spinneret, the starting position of cooling air blowing, the length of cooling air blowing, the speed of cooling air, etc., but the influence of the spinning take-up speed is the largest, and the spinning take-up speed is less than 4000 m / min. In this case, it is difficult to obtain a polyester undrawn yarn having a birefringence of 0.08 or more and a density of 1.370 or more.

At this time, the distance (spinning length) from the spinneret to the first take-up roll is equal to or larger than the larger value of LL1 and LL2 represented by the following formulas (1) and (2). Let it be less than or equal to LM represented by (3).

LL1 = 700−0.09V (1) LL2 = 50d + 50 + H (2) LM = 1000−0.09V (3) Here, V is the spinning take-up speed (m / min), H is the distance (cm) from the spinneret surface to the cooling air blowing position, and 10 ≦ H ≦
40, and d is the single yarn denier of the undrawn yarn after the take-up.

If the spinning length is outside the above range, single yarn breakage and breakage in the spinning and drawing steps occur frequently, and stable spinning and drawing cannot be performed. In particular, the shorter the spinning length, the easier the orientation and crystallization of the spun yarn to proceed, which is preferable in obtaining high modulus and low shrinkage characteristics. Further, when the distance H from the spinneret surface to the cooling air blowing position is less than 10 cm, the spinneret surface is affected by the cooling air, and unevenness occurs on the spun yarn, which is not preferable.
On the other hand, if it exceeds 40 cm, the cooling rate becomes too slow, and the density required for the undrawn yarn cannot be obtained.

The thus obtained undrawn yarn having an intrinsic viscosity of 0.85 or more, a birefringence of 0.08 or more, and a density of 1.370 or more is drawn 1.3 to 1.8 times. Stretch ratio is 1.
If less than three times, strength 6.0 g / d suitable for industrial material use
e or higher strength yarn cannot be obtained. Further, when the stretching ratio exceeds 1.8 times, thread breakage in the stretching step frequently occurs,
Stable production becomes impossible. This stretching may be performed in one stage, or may be performed in multiple stages. When performing multi-stage stretching, for example, the first-stage stretching ratio is set to 1.2 to 1.
Four times, the second-stage stretching ratio is 1.1 to 1.2 times, and the third-stage stretching ratio is 1.05 to 1.15 times. Further, the film may be stretched continuously after the spinning, or may be wound once and then stretched in another step. The former is superior in terms of productivity.

FIG. 1 is a schematic front view showing an example of an apparatus for carrying out the method of the present invention, wherein 1 is a spin block,
2 is a spinning pack, 3 is a spinneret, 4 is a heating cylinder, 5 is a heat insulating plate, 6 is a cooling air spinning cylinder, 7 is a cooling cylinder, 8 is an oiling roll, and 9 is a take-up roll.

A polyester having an intrinsic viscosity of 0.95 or more containing ethylene terephthalate as a main repeating unit,
It is melted by a conventional method, passed through a spinning pack 2, and then into a spinneret 3
Discharge from. By the heating cylinder 4 provided just below the spinneret,
The cooling air is blown from the cooling wind spinning tube 6 to the spun yarn Y while keeping the spinneret surface warm and controlling the cooling of the spun yarn Y with delay. In this case, the cooling air spinning tube 6
Is set to 10 to 40 cm.

The spun yarn Y is thinned and deformed in the cooling cylinder 7, cooled and solidified, applied with a spinning oil agent by the oiling roll 8, and then taken up by the take-up roll 9 at a take-up speed of 4000 m / min or more. . At this time, the distance (spinning length) L from the spinneret 3 to the take-up roll 9 is set to LL1 and LL described above.
The range is not less than the larger value of 2 and not more than the above-mentioned LM.

The thus obtained undrawn yarn having an intrinsic viscosity of 0.85 or more, a birefringence of 0.08 or more and a density of 1.370 or more is placed between the take-up roll 9 and the first drawing roll 10 by the first drawing. Between the roll 10 and the second stretching roll 11, and between the second stretching roll 11 and the third stretching roll 12, for example, 1.2 to 1.4 times, 1.1 to 1.2 times, And stretched 1.05 to 1.15 times in three steps, and further 0.93 to 1.05 between the third stretching roll 12 and the relaxing roll 13.
The fiber is relaxed or stretched twice and stretched 1.3 to 1.8 times in total, and wound around a winder 14 as a stretched yarn having a strength of 6.0 g / de or more.

The stretching temperature is preferably preheated at a relatively low temperature in order to suppress crystallization in the stretching step.
The take-up roll 9 and the first stretching roll 10 are at 40 to 80 ° C,
The second stretching roll 11 is heated to 70 to 120C. In the third stretching roll 12, a normal heat treatment is performed, for example,
Heat to 160-260 ° C. In addition, the relaxation roll 13
Is from room temperature to 240 ° C.

The polyester fiber obtained by the method of the present invention is subjected to twisting, adhesive treatment, and heat treatment according to a conventional method.
It can be effectively used as a rubber reinforcing structure such as a tire cord, a hose, a V-belt, a reinforcing cord for a conveyor belt, and the like. For example, a twist coefficient K of 2100 to 2500
(K = T · D ^1/2 , where T is the number of twists per 10 cm,
D indicates the denier of the twisted cord), two polyester fibers are ply-twisted, and an adhesive is applied.
A heat treatment is performed at 5 ° C. and a net stretch of 2.0 to 8.0% to obtain a treated cord.

[0032]

The polyester fiber which can be used as the high modulus and low shrink cord of the present invention has an intrinsic viscosity of 0.85 or more, a birefringence of 0.08 or more, and a density of 1.370.
The unstretched yarn is obtained by stretching the unstretched yarn at a ratio of 1.3 to 1.8 times. In order to obtain such a highly oriented, high-density unstretched yarn, a high speed at a take-up speed of 4000 m / min or more is required. After spinning, the spun yarn undergoes rapid thinning deformation, and then needs to be cooled and solidified.

However, when such high-speed spinning is performed,
In the spinning step and the subsequent drawing step, single yarn breakage and yarn breakage frequently occur, causing a problem that productivity is significantly reduced. The cause of the breakage and breakage of the single yarn is that as the take-up speed is increased, the fluctuation of the yarn tension in the spinning process is increased, and the unevenness between the single yarns in the degree of orientation (birefringence) is increased. Things. Therefore, if the tension fluctuation is reduced and the unevenness in the degree of orientation between single yarns is reduced, breakage and breakage of single yarns are reduced.
According to the study of the present inventors, the shortening of the spinning length is extremely effective in reducing the fluctuation in tension and making the orientation between single yarns uniform,
As a result, it was found that the result was a reduction in single yarn breakage and breakage in the spinning and drawing steps.

Further, when the spinning length is changed, the thinning deformation behavior of the spun yarn also changes. In other words, the yarn being spun is thinned and deformed by the pulling force and oriented and crystallized. However, even with the same pulling force (drawing speed), as the spinning length becomes shorter, the pulling force propagates to the upstream side closer to the spinneret. This tends to increase the stress applied to the solidification point. For this reason, even at the same take-off speed, as the spinning length becomes shorter, the orientation and crystallization are more likely to proceed, and higher modulus and lower shrinkage characteristics can be obtained.

For this reason, it is desirable that the spinning length be as short as possible, not more than the above-mentioned LM. However, if the spun yarn comes into contact with the take-up roll before the thinning deformation or cooling and solidification is completed, undesired yarn breakage and spots occur. Therefore, it is necessary to take out the spun yarn with a take-off roll after the slimming deformation is completed and the cooling and solidification is also completed, and the spinning length is equal to the distance from the spinneret surface to the slimming deformation end point. It is necessary to be larger than the larger one of the corresponding LL1 and the LL2 corresponding to the distance from the spinneret surface to the cooling solidification end point.

[0036]

The present invention will be described in more detail with reference to the following examples.

A polyethylene terephthalate chip having an intrinsic viscosity of 1.10 and a carboxyl end group concentration of 13 eq / 10 ⁶ g was melted by an extruder-type spinning machine, and a spinning temperature of about 300 ° C. was obtained by a direct spinning apparatus shown in FIG. so,
The fiber was spun from a spinneret having a hole diameter of 0.6 mm and a number of holes of 384 or 500. The discharge amount is approximately 100 denier after stretching.
Changed to 0de. Immediately below the spinneret, there was a heating area of 10 cm by a spin block. Immediately below that, a heating cylinder having the length and temperature shown in Table 1 was provided.

Immediately below the heating cylinder, a cooling air spinning cylinder having a length of 50 cm was attached via a heat insulating plate having a thickness of 2 cm.
The spun yarn was cooled by cooling air at 8.0 ° C. and 8.0 Nm 3 / min.
The blowing start position of the cooling air was as shown in Table 1. After continuously cooling the spun yarn in the cooling cylinder, a spinning oil was applied by an oiling roll, and the spun yarn was taken out at a take-up speed shown in Table 2. At this time, the distance (spinning length) from the spinneret to the take-up roll was variously changed as shown in Table 1, but the distance from the lower end of the cooling cylinder to the oiling roll and the distance from the oiling roll to the take-up roll were both 50 cm. It was constant.

Next, the yarn drawn by the take-up roll is continuously wound up without being once taken up by the first drawing roll,
The film was stretched in three stages by a second stretching roll and a third stretching roll, and relaxed by 3% with a relaxing roll, and wound up by a winder.
The temperature of each roll at this time was as follows: the take-up roll was at room temperature, the first stretch roll was 60 ° C., and the second stretch roll was 100 ° C.
℃, the third stretching roll is 240 ℃, the relaxation roll is 150 ℃
Met. In addition, the total draw ratio is such that the elongation of the drawn yarn is 10 to 10.
It was changed in accordance with the spinning take-off conditions (characteristics of the spinning take-off yarn) so as to be 13%.

[0040]

[Table 1]

[0041]

[Table 2]

Table 3 shows the properties of the undrawn yarn at the stage of being taken up by the take-up roll and the drawn yarn subjected to the stretching and relaxation treatment. In addition,
The birefringence unevenness CV between single yarns of an undrawn yarn indicates a fluctuation rate obtained by measuring the birefringence of 100 single yarns by an ordinary method and dividing the standard deviation by an average value.

[0043]

[Table 3]

Table 4 shows the occurrence of yarn breakage (spinning properties) in the spinning and drawing steps. The yarn breakage in the spinning and drawing steps is as follows.
0 times / 24 hours is represented by Δ, and 11 times / 24 hours or more is represented by x.

The stretched yarn thus obtained was added with 49T / 10
After giving a priming twist of 2 cm, the total of the two is 49 T / 10 cm
Was given, and a raw cord was prepared. The raw cord was immersed in an adhesive (RFL solution), dried in a heating furnace at 160 ° C. for 1 minute at a constant length, and subsequently subjected to a tensile heat treatment at 240 ° C. for 1 minute, and further subjected to 240% relaxation while giving 2% relaxation. A heat treatment was performed at a temperature of 1 ° C. for 1 minute to prepare a treatment code in which the elongation under a load of 4.5 kg was adjusted to about 3.8%. Table 4 shows the characteristics of this processing code. The 150 ° C. dry heat shrinkage of the treated cord is determined by JI
It measured according to SL-1017-1963 (5, 12).

[0046]

[Table 4]

As apparent from the above results, the polyester fibers produced by the method of the present invention (Experiment Nos. 3, 7, 1)
In Nos. 0 and 11), the treated cord had high modulus and low shrinkage, and there was little breakage in the spinning and drawing steps.

On the other hand, the spinning take-off speed is 4000 m
In the case of less than 1 / minute (Experiment No. 1), the birefringence and density of the undrawn yarn are low, and a cord with low shrinkage cannot be obtained. When the spinning length is longer than the LM (Experiment Nos. 2, 5, 6, and 9), yarn breakage in the spinning and drawing steps is large, stable production cannot be performed, and the shrinkage of the treated cord is relatively low. Get higher. On the other hand, when the spinning length is shorter than the larger value of LL1 and LL2 (Experiment Nos. 8 and 12)
Also, yarn breakage occurs frequently in the spinning and drawing steps, and stable production cannot be performed. In addition, when the distance H from the surface of the spinneret to the cooling air blowing start position of the cooling air spinning tube exceeds 40 cm (Experiment No. 4), the density of the undrawn yarn becomes low, and the high modulus and low shrinkage cord is not obtained. I can't get it.

FIG. 2 shows the range of the appropriate spinning length with respect to the spinning take-off speed.

[0050]

According to the method of the present invention, a polyester fiber which can be made into a high modulus, low shrinkage polyester cord can be stably produced at a high productivity with less breakage in the spinning and drawing steps. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing an example of an apparatus for carrying out the method of the present invention.

FIG. 2 is a graph showing a range of an appropriate spinning length with respect to a spinning take-off speed.

DESCRIPTION OF SYMBOLS 1 Spin block 2 Spin pack 3 Spinneret 4 Heating cylinder 5 Heat insulation plate 6 Cooling air spinning cylinder 7 Cooling cylinder 8 Oiling roll 9 Take-up roll 10 First stretching roll 11 Second stretching roll 12 Third stretching roll 13 Relaxing Roll 14 Winder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI D02J 1/22 D02J 1/22 K (56) References JP-A-63-152409 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) D01F 6/62 D01D 5/08-5/092

Claims (1)

(57) [Claims] 1. A method for producing a polyester fiber having improved dimensional stability, comprising the following steps. (A) A polyester containing ethylene terephthalate as a main repeating unit is melt-spun from a spinneret. (B) Next, a cooling air is blown onto the spun yarn to rapidly cool it,
Take off with a take-up roll. At this time, the distance from the spinneret to the first take-up roll is equal to or larger than the larger one of LL1 and LL2 represented by the following formulas (1) and (2), and LM represented by the following formula (3) The following is assumed. LL1 = 700−0.09V (1) LL2 = 50d + 50 + H (2) LM = 1000−0.09V (3) V is the spinning take-off speed (m / min), H is the distance (cm) from the spinneret surface to the cooling air blowing position, and 10 ≦ H ≦
40, and d is the single yarn denier of the undrawn yarn after the take-up. (C) The cooled yarn is drawn at a speed of 4000 m / min or more to obtain an undrawn yarn having an intrinsic viscosity of 0.85 or more, a birefringence of 0.08 or more, and a density of 1.370 or more. (D) The undrawn yarn is drawn 1.3 to 1.8 times to obtain a drawn yarn having a strength of 6.0 g / de or more.