JPH06192913A - Production of polyester fiber - Google Patents

Abstract

PURPOSE:To stably produce a polyester fiber having high strength and excellent dimensional stability with heat and suitable for industrial material on an industrial scale in high productivity. CONSTITUTION:A polyethylene terephthalate having an intrinsic viscosity of 0.8-1.1 or a polyester composed mainly of the polyethylene terephthalate is spun by melt-spinning and the undrawn yarn is taken up at a speed of >=3,000m/min and drawn at a high temperature. The above process is carried out under conditions to get fibers satisfying the following formulas (1) and (2). (1) rho>=0.57DELTAn+1.32 and (2) 0.07<=DELTAn<=0.09, wherein rho is density (g/cm<3>) and DELTAn is birefringence of the undrawn yarn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyester fiber having high strength and excellent dimensional stability against heat which is suitable for industrial materials.

[0002]

2. Description of the Related Art Polyester fibers represented by polyethylene terephthalate fibers are widely used for industrial materials, but with the increasing demand for higher performance, fibers having good dimensional stability against heat have been demanded. There is.

As a method for increasing the dimensional stability of polyester fibers against heat, there has been conventionally known a method in which an undrawn yarn having a high degree of molecular orientation is taken up by a high spinning speed and subjected to hot drawing (Japanese Patent Publication No. 63-63). −528 and 63-529
No.). In recent years, due to the demand for higher performance, a spinning speed has been further advanced, and a method of performing oriented crystallization in a spinning draft zone has been proposed. But usually
Oriented crystallized fibers have a low breaking elongation, and it is very difficult to stretch them at a high ratio necessary for increasing the strength.

For example, Japanese Unexamined Patent Publication (Kokai) No. 60-259620 proposes a method in which oriented and crystallized undrawn yarn is drawn in multiple stages. However, highly oriented undrawn yarn is drawn at a draw ratio of 2 times or more. That is operationally very difficult.

In addition, Japanese Patent Publication No. 3-21647 discloses 3000
A method has been proposed in which undrawn yarns that have been oriented and crystallized by drawing at a speed of m / min or more are drawn 1.5 to 2.0 times at a drawing start temperature of 125 ° C or more, but the breaking elongation of the drawn yarns is 7 to 8 %
The degree is extremely low, and there is a problem in operation in this case as well, and particularly when the drawing is performed at a high speed such as a spin draw method in which spinning and drawing are continuously performed, the operation is extremely difficult.

In addition to this, a method of hot drawing an undrawn yarn taken at a speed at which oriented crystallization is expected has been proposed. However, in either case, the strength is low, or the drawing is performed in a separate step at a low speed. However, a method for producing a fiber satisfying both dimensional stability and strength sufficiently on an industrial scale with high productivity has not yet been established.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a polyester fiber which is capable of producing a polyester fiber having both good dimensional stability and high strength characteristics in an industrially stable and productive manner. To provide.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, heat-stretched an oriented and crystallized undrawn yarn in a state where the degree of orientation is low to obtain high strength. It has been found that a polyester fiber having excellent dimensional stability can be obtained.

The present invention has been made on the basis of such findings, and its gist is as follows. Intrinsic viscosity
In the method of melt-spinning 0.8 to 1.1 polyethylene terephthalate or polyester based on this, drawing the undrawn yarn at a speed of 3000 m / min or more, and hot drawing, satisfy the formulas (a) and (b). A method for producing a polyester fiber, which is characterized in that (A) ρ ≧ 0.57 Δn + 1.32 (b) 0.07 ≦ Δn ≦ 0.09 [ρ represents the density (g / cm ³ ) of the undrawn yarn, and Δn represents the birefringence of the undrawn yarn. ]

The present invention will be described in detail below. The polyester in the present invention is substantially composed of polyethylene terephthalate, and may contain a third component such as a heat-resistant agent, a flame retardant, and a matting agent to the extent that the original properties of the polyester are not impaired. Polyester has an intrinsic viscosity (measured at a temperature of 20 ° C. using an equal weight mixture of phenol and tetrachloroethane as a solvent).
Must be in the range 0.8 to 1.1. When the intrinsic viscosity is lower than this range, the strength properties are inferior, and when it is higher than this range, the spinning stress is high and it is difficult to control the oriented crystallization, which is not preferable.

A feature of the present invention is that when melt-spinning a polyester, the crystallized undrawn yarn is taken out and subjected to hot drawing before the orientation of the molecules is promoted. The density and birefringence of the drawn yarn can be calculated by the above formula (a).
And (b).

The crystallinity due to oriented crystallization and the degree of orientation have a substantially proportional relationship at a spinning speed of 3000 m / min or more, and if the intrinsic viscosity of the polyester is constant, both are almost uniquely determined. Strictly speaking, however, by controlling the spinning conditions and adjusting the components in the polymer, the balance between crystallization and orientation can be controlled, and the undrawn yarn satisfying the formulas (a) and (b) is continuously heated. It has been found that the drawing results in fibers having high strength and excellent dimensional stability.

That is, by satisfying the expression (a), it becomes an undrawn yarn in which the fracture elongation remains while being oriented and crystallized. The origin of oriented crystallization that occurs in melt spinning is determined by the relationship between the temperature of the yarn and the stress applied to the yarn, and when the spinning speed is high or the melt viscosity is high, the stress applied to the yarn is The orientation becomes crystallized in a higher temperature region and becomes higher, and the degree of orientation is determined by the stress at the end of crystallization. The point of the present invention is to cause oriented crystallization in a state where the degree of orientation is not too high, in other words, to cause oriented crystallization at a position where stress is not too high.

In order for oriented crystallization to occur at low stress points, it is necessary to keep the initial stress of the yarn spun from the spinneret low and increase the subsequent stress gradient.
If the polyester has an intrinsic viscosity of 0.8 to 1.1, it is necessary to set the spinning temperature to 290 to 310 ℃ and the atmospheric temperature from the spinneret to 10 cm below to 300 to 350 ℃. It is desirable to control it. If the spinning temperature and this ambient temperature are lower than this range, the initial stress is too high,
High-speed take-up of 3000 m / min or more becomes difficult, and if the spinning temperature and the ambient temperature are higher than this range, the subsequent cooling will be incomplete, the orientation crystallization will be delayed, and highly oriented unstretched. It becomes a thread. Furthermore, it is necessary to set the ambient temperature 30 to 70 cm below the spinneret, where the occurrence of oriented crystallization is expected, to 60 ° C or lower. As a cooling method, it is desirable to blow cooling air of 10 to 25 ° C. at a wind speed of 60 m / min or more over a length of 20 cm or more. When a yarn with a large fineness is drawn at a high speed, the amount of heat carried by the yarn is large and at the same time a large amount of high temperature airflow in the upper part is accompanied by the yarn, so it is difficult to cool to the above temperature. It is desirable to efficiently exchange heat with the outside air, such as adjusting the air flow, between the heating cylinder and the cooling device. By setting an extreme temperature gradient on the spinning line as described above, it becomes possible to control the crystallization and orientation as the object of the present invention.

Further, by adding a small amount of an alkali metal salt of an aromatic carboxylic acid to the polyester, it becomes possible to promote crystallization in a lower orientation. When an alkali metal salt of an aromatic carboxylic acid is contained, this becomes a nucleus for promoting crystallization in the molten polyester, and oriented crystallization occurs with a lower spinning stress than in the case of no addition. Further, this alkali metal salt of aromatic carboxylic acid has excellent dispersibility, and a small addition amount hardly impairs the strength characteristics of the fiber.

Specific examples of the alkali metal salt of aromatic carboxylic acid include terephthalic acid, isophthalic acid, benzoic acid,
Mention may be made of lithium salts, sodium salts and potassium salts of aromatic mono- or dicarboxylic acids such as salicylic acid, which can be mixed in the extruder during polyester polymerization or spinning.

An appropriate amount of the alkali metal salt of aromatic carboxylic acid added to the polyester is 0.03 to 0.50% by weight. If it is less than this range, the effect of promoting crystallization is small, and if it is more than this range, the viscosity of the polyester is low. It is not preferable because it affects strength characteristics such as deterioration.

The birefringence of the undrawn yarn must be within the range of the formula (B). If the birefringence is lower than this range, the oriented crystallization is not sufficiently promoted and the dimensional stability after stretching is deteriorated. On the other hand, if it is higher than this range, the elongation becomes too low and the draw ratio becomes low, so that the strength becomes low.

Further, the take-up speed needs to be 3000 m / min or more, preferably 3500 to 4500 m / min. If the take-up speed is lower than 3000 m / min, the spinning stress is low and the oriented crystallization does not occur.

The unstretched yarn taken up is once wound and then hot-stretched, or hot-spun by a spin-draw method in which spinning is continuously performed. The spin-draw method is preferred to improve productivity. The method of the present invention can sufficiently support high-speed drawing such as the spin draw method. The hot stretching is preferably a multi-stage stretching of two or more stages, and the heating method includes a method using a heating roller, heated steam, a heat plate, a heat box, etc., but is not particularly limited. A stretching temperature of 120 to 220 ° C is suitable, and 130
It is desirable to perform the relaxation heat treatment at a temperature of up to 250 ° C, preferably 160 to 220 ° C. In particular, when the drawing speed is 3000 m / min or more, even if a high temperature heat treatment of 250 ° C. or more is attempted, sufficient heat transfer is not achieved and the crystal structure becomes nonuniform. Therefore, set the temperature in the above range,
It is desirable to perform a relaxation heat treatment of 3 to 10%.

According to the method of the present invention, the total draw ratio is 1.5.
It is possible to produce a polyester fiber having a strength of 7 g / d or more and a dry heat shrinkage ratio at 180 ° C. of 4% or less.

[0022]

EXAMPLES The present invention will be specifically described below with reference to examples. In addition, the measuring method of the characteristic value in this invention is as follows. (a) Tensile strength Using Autograph S-100 manufactured by Shimadzu Corporation, sample length 25c
The measurement was performed under the conditions of m and a pulling speed of 30 cm / min. (b) Dry heat shrinkage According to JIS L-1017, the sample was heat-treated at 180 ° C. for 30 minutes under no tension and measured. (c) Density According to JIS L-1013, a gradient tube made of carbon tetrachloride and ligroin was used to measure at 25 ° C. (d) Birefringence index It measured by the Pelec compensator method using the POH polarization microscope.

Example 1 A polyethylene terephthalate chip having an intrinsic viscosity of 0.9 was supplied to an extruder type melt spinning machine, and the diameter was 0.5 mm.
After spinning from a spinneret having 500 spinning holes and passing it through a 10 cm long heating cylinder placed directly below the spinneret, the length is 30 cm.
The cooling air is blown from the cylindrical cooling device at 72 m / min to the yarn to cool it, and it is taken up by the heating take-up roller at 70 ° C and stretched 1.25 times between the take-up roller and the first stretching roller at 140 ° C. Then, after stretching between the first stretching roller and the second stretching roller at 200 ° C., a relaxation heat treatment of 0.97 times was performed between the second stretching roller and the heat treatment roller at 200 ° C., and then winding, 15
A polyester fiber of 00d / 500f was obtained. At that time, the spinning temperature, the heating cylinder temperature, the cooling air temperature, the take-up speed, and the total draw ratio between the take-up roller and the second draw roller were set to the values shown in Table 1, and the fibers No. 1 to 6 were set. Obtained. In addition, No. 1 and 2
Is an example of the present invention, and Nos. 3 to 6 are comparative examples. The undrawn yarn at the time when it was taken up by the take-up roller was sampled, the density and birefringence were measured, and the strength, elongation and dry heat shrinkage of the wound drawn yarn were measured. Show. N of the present invention example
In both Nos. 1 and 2, fibers having a strength of 7 g / d or more and a dry heat shrinkage of 3.5% or less were obtained. On the other hand, in No. 3, since the take-up speed was slow, Δn was low and the dry heat shrinkage rate was large. In No. 4, since Δn was too high, the draw ratio was low and the strength was low. Furthermore, No. 5
In Nos. 6 and 6, since ρ was low, the dry heat shrinkage was large.

[0024]

[Table 1]

Example 2 A polyethylene terephthalate chip having an intrinsic viscosity of 0.9 was added with 0.05% by weight of an alkali metal salt of a carboxylic acid shown in Table 2 and mixed, and the spinning temperature was 305 ° C. and the heating cylinder temperature was 330 ° C. A polyester fiber was obtained by spinning and drawing in the same manner as in Example 1 except that the cooling air temperature was 18 ° C. The results are shown in Table 2. Fibers having higher strength than Nos. 1 and 2 having the same take-up speed were obtained in Nos. 7 to 10.

[0026]

[Table 2]

The original yarns of Reference Examples Nos. 1, 7 and 9 were set in the Z direction by a ring twisting machine.
9 times / 10 cm undertwist was applied, and two twisted yarns were combined and twisted 39 times / 10 cm in the S direction to obtain a raw cord. Next, using a dipping machine manufactured by Ritzler Co., 3.5 to 4.0% of RFL liquid having a solid content of 15% by weight is applied, and a drying zone is 160 ° C. × 60 seconds, a heat treatment zone is 240 ° C. × 50.
It was processed under the condition of seconds × 2 times to obtain a dip code. Dip cord strength, tenacity retention (for tenacity of raw yarn)
Table 3 shows the results of measurement of dry heat shrinkage. Each cord had excellent strength and strength retention, and the dip treatment further improved the dry heat shrinkage.

[0028]

[Table 3]

[0029]

EFFECTS OF THE INVENTION According to the present invention, a polyester fiber having high strength and excellent dimensional stability against heat, which is suitable for industrial materials, can be industrially produced with high productivity.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location D01F 6/92 301 C 7199-3B (72) Inventor Masaru Sugawa 23 Kouji Sakura Uji, Kyoto Prefecture Unitika (72) Inventor Masatsugu Mochizuki, 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Central Research Institute

Claims (2)

[Claims] 1. A method of melt-spinning polyethylene terephthalate having an intrinsic viscosity of 0.8 to 1.1 or a polyester mainly composed of polyethylene terephthalate, drawing an unstretched yarn at a speed of 3000 m / min or more, and then hot-stretching the product, wherein ) And (b) are satisfied, The manufacturing method of the polyester fiber characterized by the above-mentioned. (A) ρ ≧ 0.57 Δn + 1.32 (b) 0.07 ≦ Δn ≦ 0.09 [ρ represents the density (g / cm ³ ) of the undrawn yarn, and Δn represents the birefringence of the undrawn yarn. ] 2. The method for producing a polyester fiber according to claim 1, wherein the polyester to be spun contains 0.03 to 0.50% by weight of an alkali metal salt of an aromatic carboxylic acid.