JPH1053921A - Production of polyester fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and efficiently produce a polyester fiber having high strength as well as high elongation. SOLUTION: This polyester fiber is produced by melt-spinning a polyester polymer composition containing 2.0-10.0wt.% of a compound of the formula, R1-O-X-O-R2 (X is an aromatic group; R1 and R2 are each a 6-18C alkyl or arylalkyl), taking up the spun fiber at a spinning speed of <=3,000m/min, drawing at a draw ratio corresponding to >=90% of the critical draw ratio, subjecting to a relaxation treatment of >=15% and winding the product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a polyester fiber having both high strength and high elongation, which is suitable for use in industrial materials, particularly for seat belts, airbags, cured meshes, and sheets for civil engineering work. It is about.

[0002]

2. Description of the Related Art Polyester fibers represented by polyethylene terephthalate are widely used not only for apparel but also for industrial use because of their various excellent properties and excellent performance versus cost. When polyester fibers are used for industrial applications, the most important property is generally the mechanical properties, that is, their strength and elongation, and as the polyester fiber is used for industrial applications, higher strength is required. -There is a growing demand for higher elongation. In particular, in the fields of seat belts and civil engineering work sheets, in order to increase the amount of energy that can be absorbed before breaking, fibers that have practically sufficient strength and a higher breaking elongation than before are desired. It is rare.

Conventionally, it has been known that the degree of polymerization of a polymer should be increased in order to increase the strength and elongation of a synthetic fiber. There is a problem that is worse.

[0004] As a method for solving the problem of the deterioration of processability and achieving high strength and high elongation by increasing the degree of polymerization of a polyester polymer, a method described in JP-A-6-17313 has been proposed. In this method, a compound compatible with polyethylene terephthalate is added to lower the melt viscosity to enable the melt spinning of polyethylene terephthalate having a high degree of polymerization. However, in this method, it is necessary to introduce the melt-spun fibers into the liquid bath, so that the equipment is enlarged, and furthermore, the spinning speed cannot be increased, so that satisfactory productivity cannot be obtained. Implementation in industrial production has been difficult.

Japanese Patent Laid-Open Publication No. Hei.
A method described in Japanese Patent No. 251610 is proposed. This method is based on a uniform heat treatment for a long time by performing a relaxation treatment with a relaxation roller while heating a yarn wound around a stretching roller of a final stretching stage using a non-contact type hot plate. The purpose is to sufficiently relax the yarn and thereby obtain a yarn with low dry yield and high elongation. However, in this method, at the time of yarn breakage, there is a problem that the fusion of the yarn to the non-contact type hot plate easily occurs, and therefore, productivity and workability are poor.

As a method for producing polyester fibers for high strength and high elongation, a method for modifying polyester with additives has been proposed in Japanese Patent Application Laid-Open No. Hei 7-11512. This method improves the elongation by kneading fine particles by adding solid fine particles and a glass transition point depressant to polyester, and furthermore, a good spinning due to the synergistic effect of the fine particles and the glass transition point depressant added as an auxiliary agent. It is intended to obtain the nature. However, in this method, although high elongation can be achieved by adding solid fine particles, strength is conversely reduced by the addition of solid fine particles, and high elongation is achieved while maintaining sufficient strength. I couldn't do that.

[0007]

As described above, various production methods have been proposed to achieve high strength and high elongation of polyester fiber. It has been difficult to stably and efficiently produce polyester fibers having both high elongation.

Accordingly, an object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a method capable of stably and efficiently producing a polyester fiber having both high strength and high elongation. is there.

[0009]

In order to achieve this object, a method for producing a polyester fiber according to the present invention comprises a compound comprising a polyester polymer having an intrinsic viscosity of 0.9 or more and comprising a compound represented by the following formula (I): Is melt-spun, and the spinning speed is 300.
After drawing at 0 m / min or less, the film is stretched at a draw ratio of 90% or more of the limit draw ratio, subjected to a relaxation treatment of 15% or more, and wound up. R1-OXOR2 (I) (wherein, X is an aromatic group, and R1 and R2 each have 6 to 1 carbon atoms)
8 represents an alkyl group or an arylalkyl group. )

In order to obtain a polyester fiber having high strength and high elongation, it is effective to apply a relaxation treatment at a high relaxation rate after stretching at a high draw ratio. Although it is desired, for industrial production, it is also necessary to suppress yarn breakage during drawing to a certain level or less, and there is a limit in increasing the draw ratio.

Therefore, in the present invention, the compound of the above formula (I) (hereinafter abbreviated as compound (I)) is used as a means for suppressing the breakage of the yarn at the time of drawing and further increasing the draw ratio. ) Is provided in a polymer.

That is, when the compound (I) is contained in the polyester-based polymer, the interaction between the polyester molecular chains in the fiber can be reduced, and the entanglement between the polyester molecular chains can be easily loosened. Breakage of the polyester molecular chain can be suppressed, and therefore, stretching at a higher magnification is possible. Further, when the drawing is performed at a high ratio of 90% or more of the critical drawing ratio under the above-mentioned action by the compound (I), many polyester molecular chains are present in the drawn fiber in a tensioned state without being cut, and the oriented crystal It is possible to achieve even higher strength by dramatically progressing. Furthermore, since such a structure is present in the fiber after being stretched at a high magnification, in the relaxation treatment performed after the stretching, the high shrinkage stress due to the strained molecular chains in the remaining unoriented crystallized portion acts. A large relaxation treatment can be performed stably, and a high elongation can be provided.

As described above, by incorporating the compound (I) into the polyester-based polymer, stretching at a high magnification becomes possible. Strength and high elongation can be simultaneously achieved.

In the present invention, the above-mentioned effects of the addition of the compound (I) and the synergistic effects of the high-magnification stretching and the relaxation treatment at a high relaxation rate make it possible to increase the strength and elongation of the polyester fiber. It can be achieved at the same time.

[0015]

Next, the method for producing a polyester fiber according to the present invention will be described in detail.

The polymer composition to be subjected to melt spinning in the method for producing a polyester fiber of the present invention is a composition mainly composed of a polyester-based polymer, and is preferably a composition mainly composed of polyethylene terephthalate. Its intrinsic viscosity needs to be 0.9 or more, and preferably 1.1 or more. If the intrinsic viscosity is less than 0.9, it is not possible to obtain the desired polyester fiber having high strength and high elongation.

Further, the composition mainly composed of the polyester polymer needs to contain 2.0 to 10.0% by weight of the compound (I) represented by the general formula (I). When this compound (I) is added to the polyester-based polymer, the interaction between the polyester molecular chains in the polyester-based polymer is reduced, the entanglement between the molecular chains is easily loosened, and the polyester molecular chain generated during stretching is reduced. The effect that cutting can be suppressed is produced. As a result of this action, the effect that the critical stretch ratio can be increased by adding the compound (I) to the polyester-based polymer is obtained.

Preferred examples of the aromatic group X in the general formula (I) are as follows.

[0019]

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The compound (I) has the following formulas (II) and (III) having good compatibility with the polyester-based polymer.
, (IV) or (V) are preferred.

[0021]

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The critical stretch ratio in the present invention can be determined by the following method. That is, in a stretching method in which the unstretched yarn obtained by melt spinning is once wound up or subsequently stretched in one or two or more stages without being wound up, stretching conditions other than the stretching ratio are kept constant. With the setting kept, only the stretching ratio is gradually increased. Then, the total draw ratio when the drawn yarn cannot be wound up stably for 5 minutes or more due to the breakage of the yarn is determined, and this is defined as the limit draw ratio.

In the composition mainly comprising a polyester-based polymer used in the method for producing a polyester fiber of the present invention, the compound (I) represented by the aforementioned general formula (I) contains 2.0 to 10.0. % By weight, 2.0%
It is preferably contained in an amount of up to 5.0% by weight. When the content is less than 2.0% by weight, the effect of containing the compound (I) is insufficient, so that the effect of reducing the interaction between molecular chains in the polyester fiber is not sufficient. Breakage of molecular chains during high-stretching cannot be sufficiently suppressed. As a result, the critical stretching ratio decreases, and high strength and high elongation cannot be achieved at the same time. In addition, 10.0% by weight
If the ratio exceeds the above range, the yarn-making properties are remarkably deteriorated due to an excessive decrease in the melt viscosity and thread breakage due to the sublimation of the compound (I), so that industrial production becomes difficult.

The compound (I) may be added before the polymerization of the polyester-based polymer, or may be added after the polymerization. It is more preferable to add the compound (I) after the polymerization from the viewpoint of avoiding a decrease in the spinnability due to thermal deterioration of the compound (I). When the compound (I) is added before the polymerization, for example, the compound (I) is added at a stage after the mixed slurry of terephthalic acid and ethylene glycol is esterified, polycondensed, and then solid-phase polymerization is performed. Good.

In the case of adding after polymerization, compound (I) in the form of powder is added at a predetermined concentration to polyester chips stored in a hopper, and then the hopper is rotated in a horizontal direction to uniformly mix. The compound (I)
Any method may be used for obtaining the containing polymer chip. Furthermore, regardless of whether the compound is added before or after the polymerization, it is preferable to sufficiently mix or knead the compound so that an uneven structure is not formed in the spun fiber.

In the method for producing a polyester fiber of the present invention, the polymer composition containing the compound (I) is subjected to melt spinning. The melt spinning machine may be a pressure melter type melt spinning machine or an extruder type. A melt spinning machine may be used. In particular, when the powdered compound (I) is added to the polyester chips after the polymerization, it is desirable to mix the polyester-based polymer and the compound (I) more uniformly during melting, so an extruder-type melt spinning machine is suitable. ing.

As described above, melt spinning may be performed by any method using a melt spinning machine suitable for the production process.
The yarn that has been melt-spun and subjected to cooling, oil supply, and the like by a conventional method must be drawn at a spinning speed of 3000 m / min or less, and particularly preferably drawn at a spinning speed of 1000 m / min or less. If the spinning speed is higher than 3000 m / min, the orientation of the undrawn yarn will be too high. Therefore, it is necessary to set a high draw ratio for the next drawing or to set a high relaxation rate during the subsequent relaxation treatment. Therefore, the polyester fiber having high strength and high elongation aimed at by the present invention cannot be obtained. However, considering that it is carried out in industrial production, the spinning speed may be as low as 30
It is preferably at least 0 m / min.

The undrawn yarn drawn at the above spinning speed may be drawn once and then drawn in another step, or may be drawn continuously without being wound by a drawing roller. In addition, the stretching step may be performed in one step or two or more steps.

In any of the stretching methods, the drawn undrawn yarn must be stretched at a high ratio of 90% or more of the critical stretch ratio, and stretched at a high ratio of 95% or more of the critical stretch ratio. Is preferred. If the draw ratio is less than 90% of the critical draw ratio, it is difficult to obtain the high-strength and high-elongation fibers aimed at by the present invention, and the polyester present in a stretched state in the stretched fibers. Actions due to the inclusion of compound (I) due to the small number of molecular chains
No effect is exhibited. That is, in the polyester fiber drawn at a draw ratio of 90% or more of the limit draw ratio, a considerable number of polyester molecular chains are present in a tension state.
The action and effect of including the compound (I) are sufficiently exhibited, and the relaxation treatment at a high relaxation rate can be stably performed.

The stretching may be carried out by a usual method in which rollers (sets) heated or not heated to a desired temperature are sequentially wound and run, and stretched between the rollers at a predetermined magnification. . For example, in the case of single-stage drawing, it is preferable to preheat the yarn to be drawn to a temperature of 700 to 150 ° C., and the draw ratio is set to 90% or more of the limit draw ratio. When performing two or more stages of stretching, the first stage stretching temperature is set to 150 ° C. or less.
It is preferable for the stretchability after the step. The first stage stretching ratio is preferably 50 to 80% of the total stretching ratio. Further, the stretching temperature in the second and subsequent stages is preferably set to a high temperature of 180 ° C. or higher.

As described above, the polyester fiber containing the compound (I) and drawn at a high draw ratio is then subjected to a relaxation treatment in order to obtain a desired high elongation. As described above, it is necessary to set a high rate of preferably 18% or more. That is, if the relaxation treatment rate is less than 15%, a desired level of high elongation cannot be obtained.

This relaxation treatment may be carried out by a usual method in which rollers (set) heated or not heated to a desired temperature are sequentially wound and run, and a predetermined relaxation rate is set between the rollers. . The relaxation treatment may be carried out using a non-contact yarn heating device or the like. In this case, the relaxation heat treatment temperature is preferably set to a higher temperature than a temperature lower by 40 ° C. than the melting point of the polymer.

After the relaxation treatment, the polyester fibers are wound up in a usual manner.

[0034]

The present invention will be described below in detail with reference to examples. The physical properties in the examples are values measured by the following methods.

A. Strength (T): Using a Tensilon tensile tester manufactured by Orientec Co., Ltd., sample length 25c
m, an SS curve is determined at a tensile speed of 30 cm / min, and the strength is calculated. B. Elongation (E): Sample length 25 cm, tensile speed 3 using "Tensilon" tensile tester manufactured by Orientec Co., Ltd.
An SS curve is obtained at 0 cm / min, and the elongation is calculated.

C. Intrinsic viscosity (IV): Intrinsic viscosity of the polymer was as follows.
The relative viscosity η of the solution in which g is dissolved is measured using an Ostwald viscometer, and determined by the following approximate expression. IV = 0.0242η + 0.2634

Examples 1 to 4 and Comparative Examples 1 to 7 In each of Examples and Comparative Examples, 90 parts by weight of polyethylene terephthalate having an intrinsic viscosity of 1.0 were added to the above-mentioned formula (II)
, Ie, 10 parts by weight of bisphenol S dioctyl ether (BPS-DOB) was powder-blended and melt-kneaded with a biaxial extruder to obtain a master chip having an intrinsic viscosity of 0.70. .

This master chip is blended with a polyethylene terephthalate chip having an intrinsic viscosity of 0.71 to obtain
Blend chips having a BPS-DOB content shown in Table 1 were obtained. The blended chips were then subjected to solid state polymerization to achieve the intrinsic viscosities shown in Table 1.

The blend chip obtained by the solid-phase polymerization was subjected to melt spinning, and was melt-spun by an extruder type melt spinning machine. The discharge amount of the polymer at that time was set so that the fineness of the single yarn after stretching was about 6d, and the discharge hole of 0.6 mmφ was set to 4 holes.
A spinneret having eight spinnerets was used, and the spinning temperature was 295 ° C.

Immediately after spinning from the spinneret, the length is 300 m.
m, after passing through the atmosphere in the heating cylinder at a temperature of 320 ° C.
After cooling with a chimney wind at a wind speed of 40 m / min and applying an oil agent, the yarn was taken up at a predetermined spinning speed, and the undrawn yarn was once wound up.

This undrawn yarn is drawn by a usual method so as to have the total draw ratio shown in Table 1, and is heat-fixed with a roll at a temperature of 235 ° C., and then heated and unheated at a relaxation rate shown in Table 1. And subjected to a relaxation treatment, and then
Winding was performed at about 500 m / min to obtain a polyester fiber of 300 d / 48 fill.

[Example 5 and Comparative Example 8] The drawn undrawn yarn was drawn by a drawing roller without being wound up once, and the same spinning process as in Example 1 was carried out except that the conditions shown in Table 1 were employed. And 300d / 48fi
1 polyester fiber was obtained. Table 1 shows the physical properties of the obtained polyester fiber.

[0043]

[Table 1]

As can be seen from the results in Table 1, according to the method of the present invention, polyester fibers having sufficiently high strength and high elongation were obtained. In contrast, Comparative Example 1 containing no BPS-DOB and Comparative Example 2 containing too little BPS-DOB
In the case of or 7, high elongation could not be achieved. Further, in the case of Comparative Example 3 in which the intrinsic viscosity was too low and in the case of Comparative Example 8 in which the spinning speed was too high, both the high strength and the high elongation were insufficient.
Furthermore, when the stretching ratio conditions were Comparative Examples 4 and 6 outside the present invention, the strength could not be increased, and in Comparative Examples 5 and 6 where the relaxation rate was too low, the elongation could not be increased.

[0045]

According to the method for producing a polyester fiber of the present invention, it is possible to obtain a polyester fiber having high strength and high elongation at low cost even with a conventional yarn-making facility.
Also, in the processes after melting and spinning, only the set levels such as the relaxation treatment rate are different from those in the conventional spinning process, so that the conventional production can be performed without increasing the size of the equipment and complicating the operation. The workability and workability can be maintained as they are.

The polyester fiber having high strength and high elongation obtained by this method for producing polyester fiber is:
Useful as various industrial fibers. For example, when used for an energy absorbing belt such as a seat belt, even the same amount of base cloth can absorb a greater impact than ever before. Further, when used for a cured mesh sheet for construction, the amount of base cloth used can be smaller than in the conventional case, so that the weight of the sheet can be reduced and workability can be improved. In addition, it is extremely useful in fields where polyester fibers having both high strength and high elongation are required, such as ropes and airbags.

Claims (5)

[Claims] 1. A polymer composition mainly comprising a polyester polymer having an intrinsic viscosity of 0.9 or more and containing 2.0 to 10.0% by weight of a compound represented by the following formula (I): After picking up at a speed of 3000 m / min or less,
A method for producing a polyester fiber, comprising: stretching at a stretching ratio of at least 90% of a critical stretching ratio, performing a relaxation treatment of at least 15%, and winding. R1-OXOR2 (I) (wherein, X is an aromatic group, and R1 and R2 each have 6 to 1 carbon atoms)
8 represents an alkyl group or an arylalkyl group. ) 2. The method according to claim 1, wherein the draw ratio is 95% or more of the limit draw ratio. 3. The method for producing a polyester fiber according to claim 1, wherein the relaxation rate during the relaxation treatment is 18% or more. 4. The method according to claim 1, wherein the polyester polymer is polyethylene terephthalate. 5. The method for producing a polyester fiber according to claim 1, wherein the spinning speed is 1000 m / min or less.