JPH06136612A - Production of polyester fiber having improved dimensional stability - Google Patents

Abstract

PURPOSE:To provide a new process for stably producing a polyester fiber capable of forming a polyester cord having high modulus and low shrinkage and suitable for industrial material in high productivity. CONSTITUTION:A polyester polymer containing polyethylene terephthalate as a main recurring unit is spun by melt-spinning, quenched by blowing cooling air and taken up. In this process, the distance (spinning length) from the spinneret to the first take-up roll is set between LM (a value determined by the shrinkage characteristics and the yarn breakage) and the larger value of LL1 (a value determined by the necking deformation end point) and LL2 (a value determined by the end point of the cooling solidification) and the fiber is taken up at a speed of >=4,000m/min to obtain an undrawn yarn having an intrinsic viscosity of >=0.85, a birefringence of >=0.08 and a density of >=1.370. The undrawn yarn is drawn at a draw ratio of 1.3-1.8 to obtain a drawn yarn having a strength of >=6.0g/de.

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 polyester fibers suitable for industrial materials, and in particular, polyester fibers having improved dimensional stability and suitable for rubber reinforcement applications such as tire cords and V-belts. The present invention relates to a method for stably producing

[0002]

2. Description of the Related Art Polyester fibers are widely used not only for clothing but also for industrial materials because they have various excellent properties. In particular, polyester fibers with high strength and excellent dimensional stability are used not only for tire reinforcement applications but also for various industrial material applications, and in recent years, increasingly higher performance has been required. There is. For example, regarding polyester fibers for tire cords, it is required to further reduce the shrinkage rate in order to improve the yield at the time of tire molding, and in order to improve the riding comfort, it is required to have a high modulus. There is. Further, when used for a large tire, 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 cords for high-load wrapped belts, high toughness and fatigue resistance fibers with large elongation are required. Is required.

In response to such quality requirements, the polyester fibers obtained by the high-speed spinning and drawing method which have been developed and put into practical use in recent years have a low shrinkage ratio. The cord can be made to have a high modulus while maintaining a low shrinkage of equal or less.

For example, JP-A-53-58032 proposes a method of starting from a highly oriented undrawn yarn, which is higher than in the prior art, and drawing the same. A tire cord using this drawn yarn is It has high modulus, low shrinkage, and fatigue resistance, and has been significantly improved compared to conventional polyester tire cords. It has excellent steering stability and riding comfort when the vehicle is running at high speeds, and unevenness during tire molding (so-called Dent bulge)
There are few, and it is becoming popular and used.

In Japanese Patent Laid-Open No. 59-168119, a spinning speed of 3100 to 4000 m / min is taken up.
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 a low shrinkage cord close to rayon, for example, having an intermediate elongation of 3.7% and a dry heat shrinkage of 1.8%. There is.

Further, in JP-A-62-69819, polyester is cooled and solidified by selecting the distance from the spinneret surface to the blowing surface of cooling air and the blowing length of cooling air within a specific range. It is described that a polyester fiber having high strength, low shrinkage, and fatigue resistance can be obtained with good drawability by performing high-speed spinning while carrying out high-speed spinning and multi-drawing the obtained undrawn yarn.

[0007]

However, even with these conventional polyester fibers, the modulus and shrinkage are insufficient as compared with rayon fibers and vinylon fibers with 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 requires a large capital investment, and it is desirable to omit this step for cost rationalization. For that reason, the shrinkage as low as that of the cord of rayon fiber or vinylon fiber is required, and the conventional polyester fiber is still insufficient because the shrinkage rate is still high.

Further, in order to obtain a polyester fiber which can have a high modulus and a low shrinkage cord, when the highly oriented undrawn yarn obtained by the high speed spinning is drawn as described above, the spinnability in the spinning process is increased. Was lost, frequent single yarn breakage and yarn breakage occurred, and many yarn breakages occurred in the drawing process, making it impossible to perform stable production with good productivity.

The present invention has been made to solve the above-mentioned problems of the prior art, and its object is to increase the polyester fiber which can be made into a rayon cord or a vinylon cord having a high modulus and a low shrinkage polyester cord. It is intended to provide a novel method which is productive and can be stably manufactured.

[0010]

The above object of the present invention is achieved by a method for producing a polyester fiber having improved dimensional stability, which comprises the following steps.

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

(B) Next, cooling air is blown to the spun yarn to quench it and the yarn 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 greater than the larger value of LL1 and LL2 represented by the following formulas (1) and (2), and the following formula (3). LM or less represented by.

LL1 = 700-0.09V ... (1) LL2 = 50d + 50 + H ... (2) LM = 1000-0.09V ... (3) However, 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, d is the single yarn denier of the undrawn yarn after being taken up.

(C) The cooled yarn is taken up 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 polyester containing 90 mol% or more, preferably 95 mol% or more of ethylene terephthalate repeating units in the molecular chain. Polyethylene terephthalate is preferable as such polyester, but it may contain 10 mol% or less, preferably 5 mol% or less of other copolymerization components. Examples of such a copolymerization component include isophthalic acid, naphthalenedicarboxylic acid, adipic acid, oxybenzoic acid, diethylene glycol, propylene glycol,
Examples include trimellitic acid and pentaerythritol. Further, such polyester may optionally contain additives such as a stabilizer and a colorant.

The polyester of the present invention is required to have an intrinsic viscosity of 0.85 or more as determined from an o-chlorophenol solution at 25 ° C. If the intrinsic viscosity is less than 0.85, the orientation and crystallization of the spun yarn will be difficult to proceed, and it will be difficult to obtain a polyester fiber that can be made into a high modulus, low shrinkage cord, which is the object of the present invention.

Further, in the present invention, the undrawn yarn has a birefringence (Δn) of 0.08 or more, preferably 0.09 or more, and a density (ρ) of 1.370 or more, preferably 1.
It must be 373 or more. Birefringence is 0.0
When it is less than 8 and the density is less than 1.370, the polyester fiber capable of having the high modulus and low shrinkage cord which is the object of the present invention cannot be obtained.

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

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

First, in the present invention, it is necessary to set the spinning take-up speed to 4000 m / min or more, preferably 4500 m / min or more. The birefringence and density of the undrawn yarn are
Although it may vary depending on the spinning temperature, heating conditions under the spinneret, starting position of cooling air, blowing length of cooling air, air velocity of cooling air, etc., the effect of the spinning take-up speed is the largest, and this take-up speed is less than 4000 m / min. Then, it becomes 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 from the spinneret to the first take-up roll (spin length) is equal to or greater than the larger value of LL1 and LL2 represented by the following formulas (1) and (2), and It is less than or equal to LM represented by (3).

LL1 = 700-0.09V ... (1) LL2 = 50d + 50 + H ... (2) LM = 1000-0.09V ... (3) However, 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, d is the single yarn denier of the undrawn yarn after being taken up.

If the spinning length is out of the above range, single yarn breakage and yarn breakage frequently occur in the spinning and drawing steps, 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, and the higher the modulus and the lower the shrinkage, which is preferable. In addition, if 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 in the spun yarn, which is not preferable.
On the other hand, when 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. The draw ratio is 1.
If it is less than 3 times, the strength is 6.0 g / d, which is suitable for industrial materials.
It is not possible to obtain high tenacity yarns of e or higher. Further, if the draw ratio exceeds 1.8 times, yarn breakage frequently occurs in the drawing process,
Stable production becomes impossible. This stretching may be performed in one step or may be performed in multiple steps. When performing multi-stage stretching, for example, the first stage stretching ratio is 1.2 to 1.
4 times, the second stage draw ratio is 1.1 to 1.2 times, and the third stage draw ratio is 1.05 to 1.15 times. Further, it may be continuously stretched after spinning, or may be once wound and then stretched in a separate 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, in which 1 is a spin block,
Reference numeral 2 is a spin 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.

Polyester having ethylene terephthalate as a main repeating unit and having an intrinsic viscosity of 0.95 or more,
Melt by a conventional method, pass through the spinning pack 2, and then spinneret 3
Discharge from. By the heating cylinder 4 provided directly below the spinneret,
Cooling air is blown from the cooling air spinning tube 6 to the spun yarn Y while keeping the spinneret surface warm and delaying the cooling of the spun yarn Y. In this case, from the surface of the spinneret 3 to the cooling air spinning tube 6
The distance H to the cooling air blowing start position is set to 10 to 40 cm.

The spun yarn Y is thinned and deformed in the cooling cylinder 7, cooled and solidified, and the spinning oil is applied 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 the above-mentioned LL1 and LL.
It is set to a value greater than or equal to the larger value of 2 and less than or equal to the above 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 first drawn between the take-up roll 9 and the first drawing roll 10. Between the roll 10 and the second draw roll 11, and between the second draw roll 11 and the third draw roll 12, for example, 1.2 to 1.4 times, 1.1 to 1.2 times, respectively. And 1.05 to 1.15 times three stages, and 0.90 to 1.05 between the third stretching roll 12 and the relaxing roll 13.
It is loosened or stretched twice, and then stretched 1.3 to 1.8 times as a whole, and wound on 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 drawing roll 10 are 40 to 80 ° C.,
The second stretching roll 11 is heated to 70 to 120 ° C. In the third stretching roll 12, a heat treatment is usually performed, and for example,
It is heated to 160-260 ° C. In addition, the relaxing roll 13
The temperature is from room temperature to 240 ° C.

The polyester fiber obtained by the method of the present invention is twisted, treated with an adhesive and heat-treated by a conventional method,
It can be effectively used as a rubber-reinforcing structure such as a tire cord, a hose, a V-belt, and a reinforcing cord for a conveyor belt. 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 yarn cord), and two polyester fibers are combined and twisted, and after applying an adhesive, 235 to 24
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 made into a high modulus, low shrinkage cord which is the object 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 above-mentioned undrawn yarn is obtained by drawing 1.3 to 1.8 times, and in order to obtain such a highly oriented and high-density undrawn yarn, a high speed of 4000 m / min or more is taken up. It is necessary to carry out spinning to cause rapid thinning deformation of the spun yarn, and then to cool and solidify.

However, when such high speed spinning is performed,
In the spinning process and the subsequent drawing process, single yarn breakage and yarn breakage frequently occur, resulting in a problem that productivity is significantly reduced. The cause of the single yarn breakage and the yarn breakage is that as the take-up speed is increased, the fluctuation of the yarn tension in the spinning process is expanded, and the inter-single yarn unevenness of the orientation degree (birefringence index) is increased. It is a thing. Therefore, if the fluctuation of tension is reduced and the unevenness of the single yarn of the orientation degree is reduced, the single yarn breakage and the yarn breakage are reduced.
According to the research conducted by the present inventors, shortening the spinning length is extremely effective in reducing tension fluctuation and homogenizing orientation between single yarns.
As a result, it has been found that the result is a decrease in single yarn breakage and yarn breakage in the spinning and drawing steps.

Further, when the spinning length is changed, the thinning deformation behavior of the spun yarn also changes. That is, the yarn during spinning is thinned and deformed by the take-up force to be oriented and crystallized, but even with the same take-up force (take-off speed), the shorter the spinning length, the more the take-up force propagates to the upstream side closer to the spinneret. It easily increases the stress applied to the solidification point. Therefore, even under the same take-up speed, the shorter the spinning length, the easier the orientation and crystallization proceed, and the higher modulus and lower shrinkage characteristics are obtained.

For this reason, it is desirable that the spinning length is as short as possible, which is equal to or less than the above LM. However, if the spun yarn comes into contact with the take-up roll before its thinning deformation or cooling and solidification is completed, yarn breakage or unevenness is generated, which is not preferable. Therefore, it is necessary to take out the spun yarn with a take-up roll after the thinning deformation and the cooling solidification are finished, and the spinning length is the distance from the spinneret surface to the thinning deformation end point. It is necessary that it is greater than or equal to 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.

Polyethylene terephthalate chips having an intrinsic viscosity of 1.10 and a carboxyl end group concentration of 13 eq / 10 ⁶ g were melted by an extruder type spinning machine, and a spinning temperature of about 300 ° C. was obtained by a spinning direct drawing device shown in FIG. so,
Spinning was performed from a spinneret having a hole diameter of 0.6 mm and a number of holes of 384 holes or 500 holes. The discharge rate is about 100 denier after stretching.
It was changed to 0 de. Immediately below the spinneret, there was a 10 cm heating region by a spin block, and immediately below that was a heating cylinder of the length and temperature shown in Table 1.

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, and 25
The spun yarn was cooled with a cooling air of 8.0 Nm @ 3 / min.
The blowing air start position of the cooling air was as shown in Table 1. After the spun yarn was continuously cooled in a cooling cylinder, a spinning oil was applied with an oiling roll and taken at the take-up speed shown in Table 2. At this time, the distance from the spinneret to the take-up roll (spinning length) was variously changed as shown in Table 1. 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. I made it constant.

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

[0040]

[Table 1]

[0041]

[Table 2]

Table 3 shows the characteristics of the undrawn yarn and the drawn and relaxed drawn yarn at the stage of being taken up by the take-up roll. In addition,
The birefringence index CV between single yarns of the undrawn yarn represents a variation rate obtained by measuring the birefringence index of 100 single yarns by a conventional method and dividing the standard deviation by the average value.

[0043]

[Table 3]

Table 4 shows the occurrence of yarn breakage (spin-making property) in the spinning and drawing steps. Regarding the yarn breakage in the spinning and drawing steps, the number of occurrences of yarn breakage is 5 times / 24 hours or less, and 6 to 1
0 times / 24 hours is represented by Δ, and 11 times / 24 hours or more is represented by x.

The drawn yarn thus obtained had 49T / 10.
cm Twisted and then the two are combined to 49T / 10cm
The twist was given and the raw cord was made. The raw cord was dipped in an adhesive (RFL solution), dried in a heating furnace at 160 ° C. for a fixed length of 1 minute, and then subjected to a tension heat treatment at 240 ° C. for 1 minute to give a further relaxation of 2% and 240 A heat treatment was performed at 1 ° C. for 1 minute to prepare a treated cord having an elongation at 4.5 kg of about 3.8%. The characteristics of this processing code are shown in Table 4. The 150 ° C dry heat shrinkage of the treated cord is JI
It measured based on SL-1017-1963 (5, 12).

[0046]

[Table 4]

As is clear 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 a high modulus and a low shrinkage, and the yarn breakage in the spinning and drawing processes was small.

On the other hand, the spinning take-up 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. Further, when the spinning length is longer than the LM (Experiment No. 2, 5, 6, 9), there are many yarn breakages in the spinning and drawing steps, stable production cannot be performed, and the shrinkage rate of the treated cord is relatively high. Get higher On the other hand, when the spinning length is shorter than the larger value of LL1 and LL2 (Experiment No. 8 and 12)
However, yarn breakage frequently occurs 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 cylinder exceeds 40 cm (Experiment No. 4), the density of the undrawn yarn becomes low, and the high modulus, low shrinkage cord is I can't get it.

A summary of these results and the range of the proper spinning length with respect to the spinning take-up speed are shown in FIG.

[0050]

Industrial Applicability According to the method of the present invention, a polyester fiber which can be a high modulus, low shrinkage polyester cord can be produced stably with high productivity by reducing yarn breakage during spinning and drawing steps. be able to.

[Brief description of 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-up speed.

[Explanation of symbols]

 1 Spin Block 2 Spin Pack 3 Spinneret 4 Heating Cylinder 5 Heat Insulating 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

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Claims (1)

[Claims] 1. A method for producing a polyester fiber having improved dimensional stability, which comprises the following steps. (A) A polyester containing ethylene terephthalate as a main repeating unit is melt-spun from a spinneret. (B) Then, the spinning yarn is blown with cooling air to quench it,
Collect with a take-up roll. At this time, the distance from the spinneret to the first take-up roll is greater than or equal to the larger value of LL1 and LL2 represented by the following formulas (1) and (2), and LM represented by the following formula (3). Below. LL1 = 700-0.09V ... (1) LL2 = 50d + 50 + H ... (2) LM = 1000-0.09V ... (3) However, V is the take-up speed (m / min), H is the distance (cm) from the spinneret surface to the cooling air blowing position, and 10 ≦ H ≦
40, d is the single yarn denier of the undrawn yarn after being taken up. (C) The cooled yarn is taken up 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.