JPH06136614A - Polyester fiber having improved dimensional stability and its production - Google Patents

Abstract

PURPOSE:To provide a polyester fiber giving a polyester cord having high modulus and low shrinkage and suitable for industrial material use and to provide a new process for stably producing the fiber at a relatively low take-up speed. CONSTITUTION:This polyester fiber having an intrinsic viscosity of >=0.85, a strength of >=6.0g/de, a crystal volume of >=4.0X10<5>Angstrom <3>, a crystal melting point of >=265 deg.C, an amorphous orientation degree of 0.35-0.55 and improved dimensional stability is composed of a polyester produced by copolymerizing 0.01-1.0mol% (based on terephthalic acid) of a >=3-functional compound having carboxyl group to a polyester containing ethylene terephthalate as a main recurring unit. The present invention also relates to a process for producing the fiber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester fiber suitable for industrial materials and a method for producing the same, and in particular, it has improved dimensional stability and is suitable for rubber reinforcing applications such as tire cords and V-belts. The present invention relates to a polyester fiber and a method for stably producing the fiber.

[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.

[0006]

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 an object thereof is to provide a polyester fiber which can be a high modulus, low shrinkage polyester cord close to that of rayon cord or vinylon cord. Especially.

Still another object of the present invention is to provide a novel method capable of stably producing the above polyester fiber with high productivity.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above object, and as a result, have found that a polyester containing ethylene terephthalate as a main repeating unit is
The present inventors have found that a polyester obtained by copolymerizing a small amount of a compound having a trifunctional or higher functional carboxyl group may be subjected to high-speed spinning and stretching, and thus arrived at the present invention.

That is, according to the present invention, a polyester having ethylene terephthalate as a main repeating unit is copolymerized with a compound having a trifunctional or higher functional carboxyl group in an amount of 0.01 to 1.0 mol% based on terephthalic acid. It is made of polyester and has an intrinsic viscosity of 0.85 or more, a strength of 6.0 g / de or more, a crystal volume of 4.0 × 10 ⁵ cubic angstroms or more, a crystal melting point of 265 ° C. or more, and an amorphous orientation degree of 0.35. It is a polyester fiber having improved dimensional stability, characterized in that it is 0.55 to 0.55. Further, a polyester having ethylene terephthalate as a main repeating unit is added to terephthalic acid 0.01 to 1.
2500 mol / m of a polyester having an intrinsic viscosity of 0.90 or more copolymerized with 0 mol% is melt-discharged from a spinneret.
At a take-up speed of min-6000 m / min, then 1.
It is a method for producing a polyester fiber with improved dimensional stability, which is characterized in that the polyester fiber is stretched 4 to 2.0 times.

The polyester fiber in the present invention is a compound having an ethylene terephthalate unit as a main repeating unit, preferably a compound containing 99 mol% or more of ethylene terephthalate repeating units in the molecular chain, and a compound having a trifunctional or higher functional carboxyl group. Of 0.01 to 1.0 mol% based on terephthalic acid. Such polyesters may further contain small amounts of other difunctional copolymerization components such as isophthalic acid, naphthalenedicarboxylic acid, adipic acid, oxybenzoic acid, diethylene glycol, propylene glycol and the like. In addition, additives such as stabilizers and colorants may be included as necessary.

Examples of the compound having a trifunctional or higher functional carboxyl group used here include trimellitic acid,
Examples thereof include trimesic acid, hemimellitic acid, and pyromellitic acid. By copolymerizing such a compound having a trifunctional or higher functional carboxyl group, a partially crosslinked molecular structure is formed, and a polyester having a rigid and stable molecular structure even when melt-spun at a relatively low take-up speed. A fiber can be obtained, and it becomes possible to provide a polyester cord having excellent thermal stability and dimensional stability. The copolymerization amount of the compound having a trifunctional or higher functional carboxyl group used in the present invention is required to be 0.01 to 1.0 mol% based on terephthalic acid, and preferably 0.02 to 0. It is 0.05%. Copolymerization amount is 0.0
If it is less than 1 mol%, the amount of the cross-linked structure is too small to exert the effect of the present invention. If it exceeds 1.0 mol%, the molecular cross-linking proceeds too much to make fiber formation by melt spinning difficult. .

The polyester fiber of the present invention has an o
-Intrinsic viscosity obtained from chlorophenol solution is 0.8
It is necessary to be 5 or more, preferably 0.90 or more. When the intrinsic viscosity is less than 0.85, the orientation and crystallization of the spun yarn are difficult to proceed, and it is difficult to obtain the high modulus, low shrinkage cord which is the object of the present invention.

Further, the polyester fiber of the present invention needs to have a strength of 6.0 g / de or more, and if the strength is lower than this, it is unsuitable for use in industrial materials.

Further, the polyester fiber of the present invention is required to have a crystal volume of 4.0 × 10 ⁵ cubic angstroms or more. If the crystal volume is less than 4.0 × 10 ⁵ cubic angstroms, the desired low shrinkage cord cannot be obtained because the amorphous molecular chains are not sufficiently fastened and can move freely.

The crystalline melting point is related to the completeness of the crystal structure and the residual strength when the polyester fiber is subjected to high temperature treatment by dry heat or wet heat. The polyester fiber of the present invention needs to have a crystal melting point of 265 ° C. or higher, preferably 270 ° C. or higher. When the crystal melting point is less than 265 ° C., the crystal integrity is insufficient, a cord having a high modulus and low shrinkage cannot be obtained, and the strength deterioration during high temperature treatment is large, which is not practical.

Further, the degree of amorphous orientation fa is mainly related to the shrinkage rate and strength of the polyester fiber. When the degree of amorphous orientation is high, the amorphous molecular chains are in a more tense state, and when subjected to heat, the shrinkage rate becomes high. In the polyester fiber of the present invention, the degree of amorphous orientation needs to be in the range of 0.35 to 0.55, preferably 0.40 to 0.50. If this value exceeds 0.55, the desired low shrinkage cord cannot be obtained, and if it is less than 0.35, sufficient strength matching the application cannot be obtained.

In order to produce the polyester fiber of the present invention, a polyester containing an ethylene terephthalate unit having an intrinsic viscosity of 0.90 or more as a main repeating unit, which is obtained by copolymerizing the above compound having a trifunctional or higher functional carboxyl group Is melt-discharged from the spinneret by a conventional method,
00 m / min to 6000 m / min, preferably 3500 m / min
Take off at a take-off speed of min-5000 m / min. If the take-up speed is less than 2500 m / min, a low shrinkage cord comparable to that of rayon cord cannot be obtained, and if it exceeds 6000 m / min, the spinnability is deteriorated and yarn breakage frequently occurs in the spinning and drawing steps.

The spun unstretched yarn thus collected is stretched 1.4 to 2.0 times. If the draw ratio is less than 1.4 times, it is not possible to obtain a high tenacity yarn having a strength of 6.0 g / de or more suitable for use in industrial materials. On the other hand, if the draw ratio exceeds 2.0, yarn breakage frequently occurs in the drawing process, making stable production impossible. This stretching may be performed in one step or may be performed in multiple steps. Further, it may be continuously stretched after spinning, and once wound,
You may draw in another process. The former is superior in terms of productivity.

The polyester fiber obtained by the method of the present invention is used for industrial materials as it is, after being knitted and knitted as it is, or after heat treatment. Further, 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 after being subjected to a twisted yarn, an adhesive treatment, and a heat treatment by a conventional method.

Each characteristic of the polyester fiber in the present invention is measured by the following method.

1. Crystal volume Calculated from the following formula. Crystal volume = a-axis direction crystal size × b-axis direction crystal size ×
Long Period Interval × Crystallinity Here, the crystal size was calculated from Scherrer's formula by obtaining the half-value width of the interference peak of the (010) (100) plane. The long-period interval is determined by a conventionally known method using a small-angle X-ray scattering measurement device, that is, using a CuKα ray having a wavelength of 1.54 Å as a radiation source and irradiating the fiber axis at a right angle to obtain a Bragg diffraction line from meridional interference. It calculated using the formula of. The crystallinity was calculated by Sakurada and the warm product method.

2. Crystal melting point Using Perkin Elmer DSC-1 type, temperature rising rate 20
The melting point was measured at ° C / min, and the endothermic peak value was defined as the crystal melting point.

3. Amorphous degree of orientation fa Robert J. Samuel, Journal of Polymer Science
ence) A2, 10, 1972. That is, Δn = XfcΔnc + (1−X) faΔ
In na, Δn is a parameter indicating the degree of orientation of molecules in the filament, and was obtained by a retardation method using bromnaphthalene as an immersion liquid and a Berek compensator (for details, see Kyoritsu Shuppan "Polymer"). Experimental science course, physical properties of polymers "). X is crystallinity,
It was determined from the density by a conventional method. fc is the degree of crystal orientation, which was determined by the usual method from the average orientation angle θ measured by wide-angle X-ray diffraction. Δnc and Δna are crystalline and amorphous intrinsic birefringence,
0.22 for polyethylene terephthalate
0 and 0.275.

[0026]

In the polyester fiber of the present invention, a polyester having an ethylene terephthalate unit as a main repeating unit is copolymerized with a compound having a trifunctional or higher functional carboxyl group to partially form a linear polyester molecular chain. A molecular crosslinked structure is formed. When such a polyester partially having a molecular cross-linking structure is melted and discharged from the spinneret and taken out, the molecular cross-linking structure serves as a nucleus to promote orientation and crystallization, and a normal molecular cross-linking structure-free structure is obtained. Compared with polyester, undrawn yarn having high oriented crystallinity and large crystal size can be obtained even at a relatively low take-up speed. By stretching this unstretched yarn, a structure in which the crystal has a large developed crystal and the degree of orientation of the amorphous part is relatively small, that is, the amorphous molecular chain in a relatively relaxed state was grown to a large rigidity. It is possible to obtain a polyester fiber having a rigid and stable molecular structure that is firmly fixed to the crystal, and it is possible to provide a polyester cord having excellent thermal stability and dimensional stability.

Furthermore, since the take-up speed can be lowered, yarn breakage in the spinning and drawing steps is reduced, and the manufacturing equipment can be simplified and the cost can be reduced.

[0028]

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

100 parts of dimethyl terephthalate, 59 parts of ethylene glycol, manganese acetate tetrahydrate 0.032
Part (0.025 mol% relative to dimethyl terephthalate)
Was charged into a transesterification reaction vessel, the temperature of this reaction product was raised from 150 ° C. to 220 ° C. in a nitrogen gas atmosphere for 3 hours and a half, and the transesterification was performed while distilling off the methanol produced in the reaction vessel out of the system. The reaction was carried out. After the completion of the transesterification reaction, 0.023 parts (0.027 mol% relative to dimethyl terephthalate) of 50% ethylene glycol slurry of phosphoric acid was added as a stabilizer to the reaction mixture. Then, after 10 minutes, 0.042 parts of antimony trioxide (0.028 mol% relative to dimethyl terephthalate) was added to the reaction mixture, and after a further 10 minutes trimellitic anhydride or pyromellitic anhydride was added to dimethyl terephthalate. On the other hand, it was added at the ratio shown in Table 1, and the temperature was raised to 240 ° C. while distilling off excess ethylene glycol. After that, the reaction mixture was transferred to a polymerization reaction vessel, and it took 1 hour from 760 mmHg to 3 m.
Gradually reduce the pressure to mHg and raise the temperature to 285 ° C.
Polymerization was continued for 1 hour and 20 minutes. The obtained polymer was made into chips by a conventional method to obtain chips having an intrinsic viscosity of 0.63.

Put the chips in a tumbler type dryer,
Solid phase polymerization was carried out at a temperature of 235 ° C. and an internal pressure of 1.0 Torr for 15 hours to obtain chips having an intrinsic viscosity of 1.0.

The chips thus obtained were melted by an extruder type spinning machine and spun at a spinning temperature of about 300 ° C. from a spinneret having a pore size of 0.6 mm or 1.4 mm and 500 holes. The discharge amount was changed so that the denier after drawing was 1500 de, depending on the spinning take-up speed and the draw ratio. Immediately below the spinneret, a heating cylinder having the length shown in Table 1 was provided and heated to 320 ° C.

Immediately below the heating cylinder, cooling air of 25 ° C. and 7.0 Nm ³ / min was blown onto the spun yarn over a length of 400 mm to cool and solidify. Then, a spinning oil was applied with an oiling roll, and the oil was taken at the take-up speed shown in Table 1.

The yarn taken up by the take-up roll is continuously wound without being once wound, and is continuously drawn in three stages by the first draw roll, the second draw roll and the third draw roll, and 3% by the relaxation roll.
It was loosened and wound up with a winder. At this time, the temperature of each roll was room temperature for the take-up roll, 80 ° C. for the first stretching roll, 120 ° C. for the second stretching roll, and 230 ° C. for the third stretching roll. In addition, the total draw ratio is changed according to the spinning take-off conditions (characteristics of the spinning take-up yarn) so that the elongation of the drawn yarn is 10 to 14%, and the total draw ratio is between the take-up roll and the first drawing roll. Is 1.02 times, and the ratio between the first stretching roll and the second stretching roll is 80% of the total stretching ratio,
The stretching ratio was distributed so that the rest was stretched between the second stretching roll and the third stretching roll.

[0034]

[Table 1]

Tables 2 and 3 show the properties of the obtained drawn yarn and the situation of yarn breakage (spin-making property) in the spinning and drawing steps.
The number of occurrences of yarn breakage is 5 times /
24 hours or less is represented by O, 6 times / 24 hours or more is represented by X.

[0036]

[Table 2]

[0037]

[Table 3]

The drawn yarn thus obtained had 40T / 10.
cm Twisted and then 40T / 10cm in total
The twist was given and the raw cord was made. This raw cord was dipped in an adhesive (RFL solution) and subjected to a tension heat treatment at 240 ° C. for 2 minutes to prepare a treated cord having a tensile elongation of about 3.5% under a load of 6.75 kg. 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).

[0039]

[Table 4]

As is clear from the above results, the polyester fibers of the method of the present invention (Experiment Nos. 2, 3, 5-7, 10)
The processed cord had a high modulus and a low shrinkage, and there were few yarn breakages in the spinning and drawing steps.

[0041]

INDUSTRIAL APPLICABILITY The polyester fiber of the present invention has remarkably good dimensional stability and can be used as a cord having a high modulus and low shrinkage characteristic comparable to rayon and vinylon, and has higher strength and higher strength than rayon. It is tough and has excellent durability. In particular, when the polyester fiber of the present invention is used as a tire cord, the shrinkage rate is low, rayon can be substituted, and the post-cure inflation step performed in the tire manufacturing process can be simplified. be able to.

Further, according to the method for producing a polyester fiber of the present invention, a polyester fiber having a high modulus and a low shrinkage cord can be produced at a take-up speed which is much lower than that of the conventional one. The number of yarn breakages in the drawing step can be reduced, high productivity and stable production can be achieved, and the production equipment can be simplified and the cost can be reduced. .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaki Umeda 77 Kitayoshida-cho, Matsuyama-shi, Ehime Prefecture Teijin Limited Matsuyama Office

Claims (2)

[Claims] 1. A polyester having ethylene terephthalate as a main repeating unit, and a compound having a trifunctional or higher functional carboxyl group, added to a polyester having a terephthalic acid content of 0.1.
It is made of a polyester copolymerized with 01 to 1.0 mol% and has an intrinsic viscosity of 0.85 or more and a strength of 6.0 g / d.
e or more, crystal volume 4.0 × 10 ⁵ cubic angstroms or more, crystal melting point 265 ° C. or more, amorphous orientation degree 0.3
Polyester fiber with improved dimensional stability, characterized in that it is between 5 and 0.55. 2. A polyester having ethylene terephthalate as a main repeating unit, and a compound having a trifunctional or higher functional carboxyl group are added to a polyester having a terephthalic acid of 0.1.
A polyester having an intrinsic viscosity of 0.90 or more copolymerized with 01 to 1.0 mol% of 0.90 or more is melted and discharged from the spinneret, and then 2
Take off at a take-off speed of 500 m / min-6000 m / min,
A method for producing a polyester fiber with improved dimensional stability, which comprises drawing 1.4 to 2.0 times.