JPH0377287B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a high-strength polyethylene terephthalate yarn useful as an industrial material, and particularly to a method for producing a polyethylene terephthalate yarn having high strength and excellent mechanical fatigue properties and useful as a tire cord. Polyethylene terephthalate yarn has a high initial modulus, good dimensional stability, and satisfies the required characteristics as a carcass material for radial tires for automobiles, so its usage has been increasing recently. High-strength polyethylene terephthalate yarn is produced by melt-spinning high-molecular-weight polyethylene terephthalate, as typified by Japanese Patent Publication No. 41-7892, and then slowing the process using a heating cylinder at a temperature of about 270°C or higher, preferably about 300°C or higher. Cooling is performed, the spinning tension is controlled to provide extremely small molecular orientation corresponding to an optical birefringence of 3 x 10 ^-3 or less, preferably 2 x 10 ^-3 or less, and then stretched by a factor of 5.7 or more. It is known that the yarns thus produced are high-strength filaments having the properties as disclosed, for example, in Japanese Patent Publication No. 53-1367. On the other hand, high-strength polyethylene terephthalate yarns such as those disclosed in Japanese Patent Publication No. 53-1367 obtained by the method described in Japanese Patent Publication No. 41-7892 mentioned above are
As mentioned in Publication No. 58031, the hysteresis loss (hereinafter referred to as "work loss") is large, and as the tire rotates, the polyethylene terephthalate cord that acts as a fibrous reinforcing material generates heat, which shortens the life of the tire. It is also known to be significantly shortened. For example, in Japanese Patent Application Laid-Open No. 53-58031,
JP-A No. 1367 discloses a high-strength polyester yarn that improves the defects of the polyethylene terephthalate yarn and has a significantly stable internal structure with less work loss.
Publication No. 58032 describes a method for producing such yarn. The outline of the method described in JP-A-53-58032 is to melt-spun polyester and then uniformly quench it through a curing zone to obtain a relatively high birefringence of 9×10 ^-3 to 70×10 ^-3 . Control the yarn tension to have
Next, it is stretched. However, JP-A-53-58031 and JP-A-Sho
As described in the Examples of Publication No. 53-58032,
The strength of the yarn obtained by such highly oriented spinning is
It is about 7.3 to 9.1 g/d, which is not necessarily high. Even after additional experiments by the present inventors, it was difficult to obtain a yarn with sufficient strength. The present inventors have developed yarns with high strength and small work loss (i.e.
While conducting intensive research to obtain polyethylene terephthalate yarn (with excellent mechanical fatigue resistance),
By manufacturing yarn that satisfies special constituent requirements by a method that combines special constituent requirements,
The present inventors have discovered that the deficiencies of the prior art described above can be overcome at the stage of making a tire cord, and that characteristics particularly useful as a tire cord can be obtained, leading to the completion of the present invention. The method for producing high-strength polyethylene terephthalate yarn according to the present invention includes: (a) polyethylene terephthalate having an intrinsic viscosity of 0.60 to 0.85 is continuously spun in a molten state through a spinneret having multiple holes to form a molten multifilament; (b) This molten multifilament is passed through a 20 to 80 cm long heat retention area provided directly below the spinneret and maintained at an ambient temperature of 80 to 200°C to suppress rapid cooling, and (c) Passed through this heat retention area. The molten multifilament is rapidly cooled to turn it into a solid multifilament, and (d) this solid multifilament is
Take-off birefringence +3 at take-off speed of m/min
×10 ^-3 to +8 × 10 ^-3 finely oriented multifilament. A first stage drawing is carried out, and then multi-stage drawing is carried out at a total drawing ratio of 4.3 to 6.2 times using a pair of godet rolls heated to 20 to 140°C, and then (f) this drawn multifilament is heated to 200 to 245°C.
This is a method for producing high-strength polyethylene terephthalate yarn, which is characterized by continuous heat treatment at °C and winding. In order to make it easier to understand the difference between the method of the present invention and the conventional method, comparative data is shown in Table 1. 1st
In the table, the conventional method (1) is
The method described in Japanese Patent Publication No. 7892/1983 and the conventional method (2) are the methods described in Japanese Patent Publication No. 7892/1983.

【table】

[Table] Through the combination of manufacturing conditions described above, we have created a new high-strength polyethylene terephthalate yarn that has high strength and good mechanical fatigue properties and is useful for tire cords, which has never been seen before. can be manufactured. The new high-strength polyethylene terephthalate yarn produced by the method of the present invention is as follows (a) to (g).
It has all the characteristics listed in. (i) Intrinsic viscosity: 0.60 to 0.80, (b) Strength: 8.0 to 10.0 g/d, (c) Birefringence: 0.180 to 0.205, (d) Shrinkage measured at 175°C in air: 7.5 to 9.5%, (E) When repeated cycles of elongation and relaxation at stresses between 0.60 g/d and 0.05 g/d, the strain rate is 1 cm/d for a 25 cm long yarn standardized to 1000 total denier multifilament yarn. Work loss at 150°C measured in minutes: 0.030 to
0.060Kg・cm, (f) When repeated cycles of stretching and relaxation at a stress between 0.60g/d and 0.05g/d, a 25cm length of yarn standardized to 1000 total denier multifilament yarn Stability determined by taking the reciprocal of the product obtained by multiplying the work loss (Kg cm) at 150°C measured at a strain rate of 1 cm/min by the shrinkage (%) measured at 175°C in air. Coefficient: 1.7 to 4.5.
The book is given the same number of ply twists as the ply twists and in the opposite direction to form a ply-twisted cord, and this ply-twisted cord has 0.18 g/d.
Heat to 220℃ while applying tension of 95℃ on a hot plate.
When the model code is heat set for seconds and subjected to repeated cycles of stretching and relaxation at stresses between 0.60 g/d and 0.05 g/d, it is standardized to a multifilament yarn of 1000 total denier. Work loss at 150℃ measured on a 25cm long yarn at a strain rate of 1cm/min:
0.015 to 0.040Kg・cm. In order to make it easier to understand the difference between the high-strength polyethylene terephthalate yarn having the above-mentioned characteristics obtained by the method of the present invention and the yarn obtained by the conventional method, comparative data is shown in Table 2.

【table】

[Kg・cm/cycle/1000 denier・25cm]

Where, Wtc = Weight of cut curve [g] FSL = Full scale load [Kg] CHS = Crosshead speed [cm/min] Wt _T = Weight of paper area generated in 1 minute due to full scale load [g] W = Loss of work. The work loss of the yarn obtained as described above is 0.030 to 0.060 for the yarn obtained by the method of the present invention.
Kg/cm. If this range is smaller than the lower limit, it will be difficult to industrially produce yarn with sufficient strength, and if it is larger than the upper limit of this range, it will be difficult to produce tire cords with low work loss. Can not. A first twist is applied to the multifilament with a twist coefficient of 15800 to create a first twisted cord, and two first twisted cords are given the same number of twists as the first twist in the opposite direction to form a second twisted cord, and this first twisted cord is 0.18. The work loss of a model cord obtained by heat setting on a hot plate heated to 220° C. for 95 seconds while applying a tension of g/d can also be determined in the same manner as the work loss of a multifilament yarn. Here, the twist coefficient is K in the following formula, where the total denier is D and the number of twists is T [times/m].
is required. K=T×√ For example, total denier 1000, twist coefficient 15800
In this case, the number of twists T=500 times/m. The work loss of the twisted cord obtained in this way is 0.015 to 0.040 kg・for the yarn obtained by the method of the present invention.
cm. Cords that are smaller than the lower limit of this range and have high strength are difficult to manufacture industrially, and conversely, when the cord is larger than the upper limit of this range, the work loss of the tire cord becomes large. Mechanical fatigue properties deteriorate rapidly. Here, in Table 2 above, the 150°C work loss (Kg cm) of the model code of conventional yarn (1) and conventional yarn (2)
Although it is not clear because they are not described in the above-mentioned patent publication, the work loss of the model cord of conventional yarn (1) is around 0.014 kg cm as described in Comparative Example 3 described later. It is estimated that
The work loss of the model cord of conventional yarn (2) is estimated to be around 0.052 Kg·cm, as described in Comparative Example 4 below. Conventional thread (1) cord
Although the work loss at 150℃ is good, the strength is not sufficient.
Further, although the cord of the conventional yarn (2) has sufficient strength, it is expected that the work loss is large and the mechanical fatigue resistance is poor. The stability factor is given by repeated cycles of stretch relaxation at a stress between 0.60 g/d and 0.05 g/d.
A strain rate of 1 cm/cm for a 25 cm long yarn standardized to 1000 total denier multifilament yarn.
Take the reciprocal of the product obtained by multiplying the work loss (Kg cm) of the multifilament yarn at 150℃ measured in minutes by the shrinkage (%) of the multifilament yarn measured at 175℃ in air as described above. It is required by In the case of yarns obtained by the method of the invention, the stability coefficient is between 1.7 and 4.5. If the value is less than the lower limit of this range, it will be difficult to produce a yarn with good mechanical fatigue resistance, and conversely, if the value is greater than the upper limit of this range, it will be difficult to manufacture a yarn with sufficient strength. It cannot be manufactured on a regular basis. The yarn obtained by the method of the present invention has all the characteristics described above, and, quite unexpectedly, when such yarn is subjected to dip treatment and made into a tire cord, , the work loss specifically decreased further to 0.013 to 0.030,
For the first time, a cord with good mechanical fatigue resistance and high strength can be obtained. Next, the method of the present invention for manufacturing such a unique high-strength polyethylene terephthalate yarn will be explained in detail and specifically using the drawings. FIG. 1 shows a layout of equipment suitable for carrying out the method of the invention. Polyethylene terephthalate having an intrinsic viscosity of 0.60 to 0.85 is continuously spun in a molten state through a spinneret 1 having multiple holes to form a molten multifilament. This molten multifilament is formed in an atmosphere temperature of 80 to 200°C and a length of 20 to 80 cm in a heat insulating tube 2 installed directly below the spinneret 1.
It passes through the heat retention area to suppress rapid cooling.
The heat retaining cylinder 2 is usually formed by providing a heat retaining wall made of asbestos board, asbestos, etc. on the outside of an inner cylinder having high thermal conductivity such as aluminum or brass. Normally, the ambient temperature in the heat retention area 3 is 80 to 200 degrees without any special heating due to heat radiation from the spinneret, molten multifilament, etc.
kept at ℃. For example, lengths made of aluminum
When spinning is performed at a spinning temperature of 290°C using a 50 cm heat-retaining tube, the atmospheric temperature within the heat-retaining area 3 can be maintained at 130°C. In this way, the ambient temperature in the heat retention area 3 can be changed by changing the spinning temperature and the length of the heat retention cylinder, but if necessary, the ambient temperature can be further adjusted by embedding cold water pipes, heaters, etc. You can do it like this. Ambient temperature is 80
℃ or when the length of the heat retention region is shorter than 20 cm, the birefringence of the multifilament drawn by the godettrol pair 6 tends to be excessive. On the other hand, when the ambient temperature is higher than 200° C. or when the length of the heat retention region is longer than 80 cm, the birefringence of the multifilament drawn by the godet roll pair 6 tends to be too small. The above-mentioned melt spinning conditions include using a heating tube of 30 to 120 cm to keep the atmosphere temperature at 270°C or higher, preferably 300°C or higher when producing conventional high-strength yarn, and especially in the case of highly oriented spinning. This is in sharp contrast to quenching using cold air at 10 to 60°C directly below the spinneret. The molten multifilament that has passed through the heat retention area 3 is then rapidly cooled by cold air at about 20°C blown from the spinning tower 4 to turn it into a solid multifilament, and after being applied with a spinning finisher by an oiling roll 5, it is spun at 500 to 1500 m/min. The first godet roll pair 6 at room temperature (approximately 20°C) rotates at a speed of
A finely oriented filament with a birefringence of +3×10 ^-3 to +8×10 ^-3 is formed. At this stage, the birefringence is +3×
If it is smaller than 10 ^-3 , the work loss of the yarn obtained after drawing becomes large, and conversely, the birefringence becomes +8
If it is larger than ×10 ⁻³ , the strength of the drawn yarn tends to decrease. The finely oriented multifilament taken up by the first pair of godet rolls 6 is first stretched by a factor of 1.01 to 1.10 using the first pair of godet rolls at room temperature without being wound up. , 8, and 9 in multiple stages. Preferably, the temperature of the second godettrol pair is
90 to 110℃, the temperature of the third godettrol pair is 120℃
The temperature should be between 140°C and 140°C. By setting such temperature conditions, a total stretching ratio of 4.3 to 6.2 can be achieved. By performing the first stage stretching of 1.01 to 1.10 times with the first godet roll pair at room temperature in this way, the subsequent godet roll pairs 7, 8, 9
The drawing operation between the two is extremely stable, and drawn yarn having a strength of 8.0 to 10.0 g/d and an elongation of 11% or more can be stably obtained uniformly and without yarn breakage. Note that one of the two rolls of the godet roll pair may be a passively driven roll such as a separate roll. If the total draw ratio is less than 4.3, yarn with sufficient strength cannot be obtained, and
If it is larger than 6.2, the yarn will break frequently, making it impossible to manufacture the yarn on an industrial scale. Here, the "total drawing ratio" refers to the ratio of the surface speeds of the fourth godet roll pair 9 and the first godet roll pair 6. The multifilament yarn drawn in multiple stages is then heat-treated with a fourth godet roll 9 heated to 200 to 245°C, and wound up as a product package 11. This heat treatment tends to reduce the dry heat shrinkage rate of the multifilament yarn as well as the work loss of the yarn. Next, the method of the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to these Examples. Example 1 A 1000 d/384 f polyethylene terephthalate yarn for tire cords was obtained by direct spinning and drawing heat treatment using the apparatus shown in FIG. That is, spinneret 1 having 384 spinning holes was used, and the intrinsic viscosity was
0.70 molten polyethylene terephthalate was spun at a spinning temperature of 290°C, and 130
The spinning tower 4 is passed through an atmosphere 3 kept at a temperature of
It is cooled and solidified by 20℃ cold air blown out.
After applying a spinning finish with an oiling roll 5, the first godet roll pair 6 rotates at 670 m/min and is at room temperature (20°C), and the second godet roll is immediately and continuously heated to 100°C without being wound up. Stretched 1.01 times between VS 7 and continuously
It was stretched 4.44 times between the third godet roll pair 8 heated to 130°C, and then heated continuously to 240°C.
4000m/min between the 4th godets troll vs. 9th
Stretched 1.34 times, total stretching ratio 6.01 times,
It was heat treated with Godetstrol pair 9 and wound up. The obtained yarn has an intrinsic viscosity of 0.68 and a strength of 9.65 g/
d, elongation 11.4%, birefringence 0.195, 175°C dry heat shrinkage 8.7%, 150°C work loss 0.055 Kg cm, stability coefficient 2.1. This yarn was twisted 500 times using a ring twisting machine. A pre-twisted cord was created by applying an S twist of /m, and a Z twist of 500 times/m was applied to the two pre-twisted cords to create a 2220d ply-twisted cord. This ply-twisted cord was subjected to tension heat treatment using the apparatus shown in FIG. 2 to create a model cord.
That is, from the supply roll 12 to the twisted cord 13
was pulled out, slid on the hot plate 14, and taken over by the transaction roll 17. In FIG. 2, all 15 are free rolls. Here the temperature of the hot plate is 220
℃, and the heat treatment time was 95 seconds. Load 800g
Using a weight of 16, apply a tension of 400 to the cord being processed.
gave g. The work loss for this model code is
It decreased significantly to 0.033Kg・cm. Furthermore, from the above ply-twisted cord, Litzler
I created a dip code using Comput-reator. The strength of the obtained dip cord is 7.0 g/d,
Work loss was further significantly reduced to 0.020Kg・cm. This dip code is JIS L-1017 1.3.2.1A
A tube fatigue test was conducted in accordance with the law. Goodyear
Using a type testing machine, a rubber tube with dip cord embedded concentrically was bent at an angle of 95° to 3.5
Applying an internal pressure of Kg/cm ²・G, the rotation speed of the tube
The tube was rotated at 850 rpm and the time until the tube burst due to dip cord fatigue was measured. As a result, the average tube rupture time was 660 minutes. Example 2 The intrinsic viscosity of polyethylene terephthalate polymer was 0.62, the spinning temperature was 283°C, and the temperature of the insulation cylinder was 120°C.
℃, the speed of the first godettrol pair is 672 m/min,
The stretching ratio between the second godet roll pair and the third godet roll pair is 3.93, and the stretching ratio between the third godet roll pair and the fourth godet roll pair is 1.50.
The same method as in Example 1 was repeated except that the total stretching ratio was 5.95, and the intrinsic viscosity was 0.61, the strength was 8.73 g/d, and the elongation was
11.1%, birefringence 0.202, 175℃ dry heat shrinkage 7.2%,
A multifilament yarn with a work loss of 0.037 Kg·cm at 150°C and a stability coefficient of 3.8 was obtained. The work loss of the model cord is 0.021Kg・cm, and the strength of the dip cord is
The tube rupture time was 6.6 g/d, the work loss was 0.016 Kg·cm, and the average tube rupture time was 850 minutes. Example 3 The intrinsic viscosity of polyethylene terephthalate polymer was 0.80, the spinning temperature was 300°C, and the temperature of the insulation cylinder was 140.
℃, the speed of the first godettrol pair is 603 m/min,
The stretching ratio between the second godet roll pair and the third godet roll pair is 4.42, the stretching ratio between the third godet roll pair and the fourth godet roll pair is 1.33,
The same method as in Example 1 was repeated except that the total stretching ratio was 5.94, and the intrinsic viscosity was 0.78, the strength was 9.93 g/d, and the elongation was
12.4%, birefringence 0.198, 175℃ dry heat shrinkage 9.4%,
A multifilament yarn with a work loss of 0.058 at 150°C and a stability coefficient of 1.8 was obtained. The work loss of the model cord is 0.037Kg・cm, and the strength of the deep cord is 7.2g/cm.
d. The work loss was 0.025 kg·cm, and the average tube rupture time was 610 minutes. Example 4 The intrinsic viscosity of polyethylene terephthalate polymer was 0.61, the spinning temperature was 283°C, and the temperature of the insulation cylinder was 120°C.
℃, the speed of the first godettrol pair is 1.351 m/min,
The stretching ratio between the second godet roll pair and the third godet roll pair is 2.32, and the stretching ratio between the third godet roll pair and the fourth godet roll pair is 1.45.
The same method as in Example 1 was repeated except that the total stretching ratio was 3.70, and the intrinsic viscosity was 0.60, the strength was 8.24 g/d, and the elongation was
11.9%, birefringence 0.186, 175℃ dry heat shrinkage 6.9%,
A multifilament yarn with a work loss of 0.032 Kg·cm at 150°C and a calculated stability of 4.5 was obtained. The work loss of the model cord is 6.018Kg・cm, and the strength of the dip cord is
The tube rupture time was 6.5 g/d, the work loss was 0.013 Kg·cm, and the average tube rupture time was 950 minutes. Comparative Example 1 When polyethylene terephthalate polymer had an intrinsic viscosity of 0.95 and an attempt was made to manufacture a multifilament yarn using a method similar to Example 1, the total drawing ratio could not be increased to 5.3 times or more, and the yarn The strength remained at 7.02 g/d. Comparative Example 2 According to the method described in Japanese Patent Publication No. 41-7892, a polyethylene terephthalate polymer with an intrinsic viscosity of 0.95 was spun at a spinning temperature of 310°C, and the mixture was placed in a 50cm long heating cylinder heated to an ambient temperature of 400°C. 393 to relax the orientation through the 393
It was taken up using the first pair of godet rolls at m/min, and continuously stretched at a total stretching ratio of 6.1 times, 2400 m/min.
I rolled it up in minutes. The intrinsic viscosity of the obtained yarn is
0.91, strength 10.5g/d, elongation 13.3%, birefringence
0.204, 175℃ dry heat shrinkage rate 12.2%, 150℃ work loss
A yarn of 0.095 Kg·cm and a stability coefficient of 0.9 was obtained. Although the work loss of the model cord is 0.052Kg・cm and the strength of the deep cord is 7.4g/d, the work loss is
High at 0.041Kg・cm, average tube rupture time is 124
It was only a minute. Comparative Example 3 Polyethylene terephthalate having an intrinsic viscosity of 0.95 was spun at a spinning temperature of 310°C in accordance with the method described in JP-A No. 53-58032, and quenched with cold air directly below the spinneret, and the rest was carried out in accordance with Example 1. , 1500m/
The film was taken up using the first pair of godet rolls at a rate of 2.5 m/min, continuously stretched to a total stretching ratio of 2.35 times, and wound at 3525 m/min. The obtained yarn has an intrinsic viscosity of 0.91 and a strength of
A yarn of 7.85 g/d, elongation 8.2%, birefringence 0.182, 175°C dry heat shrinkage 6.1%, 150°C work loss 0.016, and stability coefficient 8.2 was obtained. Model code work loss
0.014Kg・cm, deep cord strength 6.1g/d,
Work loss 0.013Kg・cm, tube rupture time average
Although the mechanical fatigue resistance is good at 990 minutes, the strength is low, and the phenomenon in which the work loss of the original multifilament, which is characteristic of the present invention, decreases significantly from the work loss when used as a dip cord has not been observed. Ta. As detailed above, the polyethylene terephthalate yarn obtained by the method of the present invention, which skillfully combines specific structural requirements, has a specific reduction in work loss and a high strength when processed as a material for tire cords. It is possible to obtain a tire cord with high strength and good mechanical fatigue resistance. Comparative Example 4 Polyethylene terephthalate having an intrinsic viscosity of 0.65 was spun at a spinning temperature of 290°C according to the method described in JP-A No. 53-58028, and the material was spun in an atmosphere kept at 210°C using a 20cm-long heat-insulating tube. Pass, 20
After cooling and solidifying by blowing cold air at a temperature of 8×10 ^-3 Nm ³ /min per gram of spinning, and applying a finishing agent with an oiling roll,
It is taken up by the first pair of godet rolls that rotate in minutes (the birefringence index of the thread at this time is 1.2 × 10 ^-3 ),
Immediately without winding up, the second godet roll pair was preheated at a speed of 420 cm/min and 95°C, and then stretched 3.6 times between the third godet roll pair that was continuously heated to 160°C. Then, after stretching 1.67 times (total stretching ratio 6.0 times) with the fourth Godet roll pair with a surface temperature of 200°C, 2520 m/
I turned it over at a speed of 1 minute. The obtained yarn has an intrinsic viscosity of 0.63 and a strength of 8.70 g/
d, elongation 10.8%, birefringence 0.201, 175°C dry heat shrinkage 9.3%, 150°C work loss 0.073 Kg·cm, and stability coefficient 1.47. Furthermore, the work loss of the model code is 0.043Kg・cm,
Deep cord strength 6.6g/d, work loss 0.034
kg・cm, and the tube rupture time was as short as 298 minutes.

[Brief explanation of drawings]

FIG. 1 is a layout diagram of a typical apparatus for manufacturing high-strength polyethylene terephthalate yarn by the method of the present invention, and FIG. 2 is a layout diagram of a typical apparatus for manufacturing model cord. DESCRIPTION OF SYMBOLS 1... Spinneret, 2... Heat insulation tube, 4... Spinning tower, 5... Oiling roll, 6-9... Godet roll pair group, 10... Multifilament yarn, 11... Winding package, 12... ... Supply roll, 13 ... Twisted cord, 14 ... Free roll,
16...Load, 17...Take-up roll.

Claims (1)

[Claims] 1. A method for producing high-strength polyethylene terephthalate yarn, comprising: (a) continuously spinning polyethylene terephthalate having an intrinsic viscosity of 0.60 to 0.85 in a molten state at 280 to 310°C through a spinneret having multiple holes; (b) This molten multifilament is passed through a heat-retaining area with a length of 20 to 80 cm maintained at an ambient temperature of 80 to 200°C provided directly below the spinneret to suppress rapid cooling; (c) The molten multifilament that has passed through this heat retention area is rapidly cooled to turn it into a solid multifilament, (d) The solid multifilament is
Take-off birefringence +3 at take-off speed of m/min
×10 ^-3 to +8 × 10 ^-3 finely oriented multifilament. A first stage of stretching is carried out, then multi-stage stretching is carried out to a total stretching ratio of 4.3 to 6.2 times using a pair of godet rolls heated to 20 to 140°C, and then (f) this stretched multifilament is heated to 200°C to 200°C without shrinking. A method for producing high-strength polyethylene terephthalate yarn, which is characterized by continuous heat treatment at 245°C and winding.