JPH0931749A - Method for producing polyester fiber - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To produce a high quality polyester fiber which is free from fluff generation and thickness unevenness and which is excellent in mechanical properties such as strength and elongation without causing yarn breakage. It is to be manufactured with high processability by the direct spinning and drawing method. SOLUTION: A fiber-forming polyester containing inorganic fine particles having an average particle diameter of 0.01 to 1.0 μm in a proportion of 0.1 to 10% by weight is melt-spun and then cooled to the glass transition temperature or lower. Then, the polyester fiber is continuously introduced into the heating zone, stretched, and then taken out at a speed of 3500 m / min or more to produce a polyester fiber.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing polyester fibers. More specifically, the present invention relates to an improved method for producing a polyester fiber stretched by a direct spinning / drawing method, and in the case of the method of the present invention, there is no occurrence of fluff or uneven thickness, Moreover, high-quality polyester fibers having excellent mechanical properties such as strength and elongation can be smoothly produced with good processability without causing yarn breakage or fluff.

[0002]

2. Description of the Related Art Polyester fiber is generally stretched and used from the standpoint of improving mechanical properties such as strength and elongation, dimensional stability, and other points. As a method for stretching the polyester fiber, a sequential stretching method in which the polyester fiber obtained by spinning is once wound, then rewound and heated / stretched, or the polyester fiber spun from the spinneret is directly wound without being wound. The two methods of direct spinning and drawing, in which the film is drawn and then wound, are widely adopted. Then, in one of the latter direct spinning drawing methods, while melt-spun polyester fibers are taken at a high speed of 4000 m / min or more, or 2000-4500 m / min (while running at a high speed), the glass is once drawn. A method is known in which the material is cooled to a temperature equal to or lower than the transition temperature, and subsequently, it is passed through a heating zone and stretched in the heating zone (Japanese Patent Publication No. 45-1932 and Japanese Patent Publication No. 55-1).
No. 0684).

In the above-mentioned direct spinning drawing method involving high-speed take-up, while the spun yarn is running in the heating zone at high speed, air resistance acts on the running yarn in the heating zone and the yarn is run. Stretching is performed by increasing the tension of the strip. Therefore, there is no need to particularly use a mechanical drawing device such as using a plurality of rollers having different rotation speeds, and there is an advantage that polyester fibers drawn by a simplified spinning / drawing device can be produced with high productivity. However, in the case of such a conventional direct drawing method involving high-speed take-up, since the draw ratio is not mechanically set using a drawing device such as a drawing roller, the temperature of the heating zone and the running of the yarn are The quality of the fiber is greatly influenced by the speed and the tension applied to the running yarn, and even if the running speed of the yarn in the heating zone or the tension applied to the running yarn is slightly changed, stretch unevenness is likely to occur, which causes It has the drawback that thread breakage, loops, fluff, and fineness unevenness are likely to occur.

[0004]

The object of the present invention is to provide a high-quality stretched product which is free from the formation of loops and fluffs, has no unevenness in fineness, is excellent in uniformity, and is excellent in mechanical properties such as strength and elongation. It is an object of the present invention to provide a method capable of producing the above polyester fiber by a direct spinning drawing method with good process stability without causing yarn breakage and the like.

[0005]

In order to achieve the above object, the inventor of the present invention has made various studies from the viewpoint of material, process, apparatus and the like. As a result, once the spun polyester fiber is once cooled to the glass transition temperature or lower, the polyester fiber is directly drawn in the heating zone by passing through the heating zone while being continuously taken at high speed to directly produce the polyester fiber. In performing the method, in the polyester as the spinning raw material, if the inorganic fine particles having a specific average particle diameter are contained in a specific ratio, the temperature of the heating zone,
Even if there are some fluctuations in the running speed of the yarn, the tension applied to the running yarn, etc., there are no loops or fluffs, and there is no unevenness in fineness, and it has excellent mechanical properties such as strength and elongation. The present invention has been completed by finding that polyester fibers can be produced with good process stability and high productivity without causing troubles such as yarn breakage.

That is, according to the present invention, the average particle size is 0.01.
After melt-spinning a fiber-forming polyester containing 0.1 to 10% by weight of inorganic fine particles having a particle size of 1.0 μm,
It is a method for producing a polyester fiber, which comprises cooling to a temperature below the glass transition temperature, subsequently introducing it into a heating zone and stretching it, and then taking it off at a speed of 3500 m / min or more.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The fiber-forming polyester used in the present invention is not particularly limited as long as it is a melt-spinnable polyester, but the fiber-forming polyester may be polyethylene terephthalate, polybutylene terephthalate, or ethylene terephthalate units and / or butylene terephthalate units. A copolyester having a main constituent unit containing a small amount of another copolymerization unit is preferable, and polyethylene terephthalate is particularly preferable.

When a copolyester mainly comprising ethylene terephthalate units and / or butylene terephthalate units is used as the fiber-forming polyester, the proportion of other copolymerized units in the copolyester is preferably 10 mol% or less. Examples of other copolymerized units in this case include aromatic carboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalene dicarboxylic acid, and 5-alkali metal sulfoisophthalic acid; oxalic acid, adipic acid,
Aliphatic carboxylic acids such as azelaic acid and sebacic acid; polyfunctional carboxylic acids such as trimellitic acid and pyromellitic acid; or carboxylic acid units derived from their ester-forming components; diethylene glycol, propylene glycol, butanediol or ethylene. Examples thereof include units derived from glycol, polyethylene glycol, glycerin, pentaerythritol and the like. The copolyester can contain one or more of the above-mentioned copolymer units.

In the present invention, the viscosity and the molecular weight of the fiber-forming polyester (hereinafter simply referred to as "polyester") used for producing the fiber are not particularly limited, and any viscosity and molecular weight that can be melt-spun can be used. I can, but
Generally, a polyester having an intrinsic viscosity [η] of 0.62 to 0.65 is used when measured at 30 ° C. in a mixed solution of phenol and tetrachloroethane using an Ubbelohde viscometer. It is preferable from the viewpoints of spinnability and physical properties of the obtained polyester fiber.

In the present invention, the polyester before spinning has an average particle size of 0.01 to 1.0 μm, as described above.
It is necessary to contain inorganic fine particles of m.
In this case, as the inorganic fine particles, any inorganic fine particles which do not have a deteriorating effect on the polyester forming the fiber and have excellent stability by themselves can be used. Representative examples of the inorganic fine particles that can be effectively used in the present invention include silica, alumina, calcium carbonate, titanium oxide, barium sulfate, and the like. These inorganic fine particles may be used alone or in 2 You may use together 1 or more types.

The inorganic fine particles to be contained in the polyester must have an average particle diameter of 0.01 to 1.0 μm, and preferably 0.03 to 0.6 μm, as described above. If the average particle size of the inorganic fine particles is less than 0.01 μm, the polyester fiber may have a slight variation in the temperature of the heating zone for stretching, the running speed of the yarn, the tension applied to the running yarn, etc. Loops, fluff, and fineness unevenness will occur. On the other hand, when the average particle size of the inorganic fine particles exceeds 1.0 μm, the stretchability of the fiber is deteriorated and the spinnability becomes poor, and the fiber breakage easily occurs during the production of the polyester fiber. Here, the average particle size of the inorganic fine particles referred to in the present invention refers to a value when measured using a centrifugal sedimentation method,
The details are described in the examples below.

As described above, in the present invention, the content of the inorganic fine particles is 0.1 based on the weight of the polyester.
~ 10.0% by weight, 0.5 ~
It is preferably 5.0% by weight. If the content of the inorganic fine particles is less than 0.1% by weight based on the weight of the polyester, slight fluctuations may occur in the temperature of the heating zone for stretching, the running speed of the yarn, the tension applied to the running yarn, etc. Even if it occurs, loops, fluffs, fineness irregularities, etc. will be generated in the obtained polyester fiber. On the other hand, if the content of the inorganic fine particles exceeds 10.0% by weight, the inorganic fine particles will be running yarns in the fiber drawing step. Makes the resistance between air and air excessive,
The process becomes unstable due to the occurrence of fuzz and yarn breakage.

The method of adding the inorganic fine particles to the polyester is not particularly limited. The inorganic fine particles may be added and mixed in such a manner that the fine inorganic particles are uniformly mixed in the polyester at an arbitrary stage immediately before melt spinning of the polyester. For example, the inorganic fine particles may be added at any time during the polycondensation of the polyester, may be added later during the production of pellets in the polyester after the polycondensation, or when melt spinning the polyester. Before the polyester is spun from the spinneret, inorganic fine particles may be uniformly melt-mixed in the polyester.

In addition to the above-mentioned inorganic fine particles, the polyester is, if necessary, a fluorescent whitening agent, a stabilizer, an antioxidant, an ultraviolet absorber, an antihydrolysis agent, an antistatic agent, a flame retardant, and a coloring agent. You may contain the 1 type (s) or 2 or more types of an agent and other additives.

Then, the above polyester containing 0.1 to 10.0% by weight of inorganic fine particles having an average particle diameter of 0.01 to 1.0 μm is melt-spun. In this case, the melt spinning temperature, the melt spinning speed, etc. are not particularly limited, and the melt spinning can be carried out under the same conditions as those usually used for producing polyester fibers. The temperature is in the range of (melting point of polyester + 20 ° C.) to (melting point of polyester + 40 ° C.) (generally about 280 to 300 ° C. in the case of polyethylene terephthalate), and the melt spinning speed (melt spinning amount) is about 20 to. 50 g / spinning hole of about 1 mm ² · min is preferable because polyester fibers of good quality can be obtained with good spinning processability. Further, the size and number of the spinning holes in the spinneret, the shape of the spinning holes, etc. are not particularly limited, and can be adjusted according to the intended single fiber fineness of the polyester fiber, the total denier number, the cross-sectional shape and the like. Generally, it is desirable to set the size of the spinning hole (single hole) to about 0.018 to 0.07 mm ² .

Then, the polyester fiber melt-spun as described above is once cooled to a temperature lower than its glass transition temperature, preferably 10 ° C. or more lower than the glass transition temperature. The cooling method and the cooling device in this case are not particularly limited as long as the method and the device can cool the spun polyester fiber to the glass transition temperature or lower, but are not particularly limited. It is preferable that a cooling air blowing device is provided, and cooling air is blown onto the spun polyester fiber to cool the polyester fiber to a temperature lower than the glass transition temperature. At that time, the cooling conditions such as the temperature and humidity of the cooling air, the blowing speed of the cooling air, and the blowing angle of the cooling air with respect to the spun fiber are not particularly limited, and the polyester fiber spun from the spinneret may be prevented from shaking. Any condition may be used as long as it can be rapidly and uniformly cooled to the glass transition temperature or lower while preventing the occurrence. Among them, generally, the temperature of the cooling air is about 20 ~
30 ° C., the humidity of the cooling air is 20 to 60%, the blowing speed of the cooling air is about 0.4 to 1.0 m / sec, and the blowing direction of the cooling air to the spun fiber is perpendicular to the spinning direction. It is preferable to cool the spun polyester fiber because high quality polyester fiber can be obtained smoothly. When cooling is performed under the above conditions using a cooling air blowing cylinder, the length is about 80 to 100 cm with or without a space just below the spinneret.
It is preferable to arrange a cooling air blowing cylinder.

Next, the polyester fiber cooled to the glass transition temperature or lower is subsequently directly introduced into the heating zone and stretched. Although the temperature of the heating zone may vary depending on the type of polyester, etc., in general, if the temperature is 40 ° C. or more higher than the glass transition temperature of polyester,
The obtained polyester fiber is preferable because it can satisfy the physical properties practically. For example, in the case of polyethylene terephthalate fiber, the temperature of the heating zone is about 10
It is preferably 0 ° C. or higher. The maximum temperature of the heating zone is
The temperature may be any temperature at which fusion between fibers, yarn breakage, single yarn breakage, and the like do not occur in the heating zone. The type and structure of the heating zone is such that the polyester fiber running in the heating zone can be heated without contacting the heating means in the heating zone and the yarn running in the heating zone and the air surrounding it. Any structure may be used as long as it can generate resistance in the fiber and increase the yarn tension to cause the fiber to be drawn. Among them, a tubular heating zone is preferably used as the heating zone, and a pipe heater having an inner diameter of about 20 to 50 mm in which the tube wall itself is a heater is particularly preferable.

The installation position of the heating zone from the spinneret, the length of the heating zone, etc. are determined by the type of polyester fiber, the amount of polyester spun, the cooling temperature of the polyester fiber, the running speed of the polyester fiber, the temperature of the heating zone, and the heating temperature. It can be adjusted according to the inner diameter of the zone, etc., but generally the distance from just below the spinneret to the inlet of the heating zone is about 0.5 to 3.0 m,
It is desirable to set the length of the heating zone to about 1.0 to 2.0 m, because the polyester fiber can be heated in the heating zone and uniformly and smoothly drawn.

If necessary, an oil agent is applied to the polyester fiber drawn in the heating zone, and then the polyester fiber is taken out at a high speed. In the present invention, it is necessary to carry out the process for producing a stretched polyester fiber comprising the above-mentioned series of steps at a polyester fiber take-up speed of 3500 m / min or more, and the take-up speed is 4000 m / min or more. preferable. Polyester fiber take-up speed is 3500m
If it is less than / minute, the drawing of the fiber in the heating zone will not be performed sufficiently, the mechanical properties of the obtained polyester fiber will be reduced, and the method of the present invention comprising the above series of steps will not be performed smoothly, In particular, fluctuations in the tension of the yarn in the heating zone, overheating, etc. occur, making it difficult to perform uniform stretching. In performing the method of the present invention,
Polyester fiber {take-off speed (m / min)} / {spun amount of polyester fiber (25 g / spinning hole 1 mm ² · min)}
The value of is preferably in the range of about 140 to 200.

In the present invention, the single fiber fineness and the total number of denier of the finally obtained polyester fiber are not particularly limited and can be appropriately adjusted depending on the use of the polyester fiber, etc. Especially the single fiber fineness is 0.
It is suitable for producing polyester fibers (polyester multifilament yarn) having a denier of 5 to 6 and a total denier of 30 to 100 denier. Further, in the present invention, the cross-sectional shape of the polyester fiber is not particularly limited, and not only ordinary round cross-section fibers, but also elliptical, triangular,
Square, polygon, hollow, multi-lobe, array, V-shaped, T
It may be a modified cross-section fiber such as a letter shape.

[0021]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. In the following examples, the average particle size of the inorganic fine particles, the spinnability of the polyester fiber, the strength, the elongation, the uniformity (Worcester spots: U%) of the finally obtained polyester fiber, and the number of fluff generated are as follows. It was measured or evaluated in this way.

Measurement of the average particle size of the inorganic fine particles : It was calculated based on the centrifugal sedimentation curve obtained by using a centrifugal particle size measuring device (“CAPA-5000 type” manufactured by Horiba Ltd.).

Spinnability of polyester fiber: 100 kg of polyester fiber was spun, the presence or absence of yarn breakage during spinning was examined, and the presence or absence of fluff was visually observed in the obtained polyester fiber. The results are shown in Table 1 below. It evaluated according to the evaluation criteria.

[0024]

[Table 1] Evaluation criteria for spinnability of polyester fibers ⊚: No yarn breakage occurred during spinning, and no fluff occurred in the obtained polyester fiber, and the spinnability was extremely good. ○: No yarn breakage occurred during spinning Although slight fluff was generated in the polyester fiber, the spinnability was almost good. Δ: When 100 kg was spun, yarn breakage occurred up to 3 times, and spinnability was poor ×: 100 kg When spun, the yarn breakage occurs more than three times, and the spinnability is extremely poor.

Strength of Polyester Fiber : The strength of the polyester fiber was determined from the load-elongation curve obtained using an Instron type tensile tester.

The elongation of the polyester fiber: Instron tensile tester load obtained using the - was determined elongation of the polyester fiber from the extension curve.

Uniformity of polyester fiber (Worcester spot:
U value) : Using a Wurster spot tester manufactured by Zellberger Co., Ltd., thread is passed between the electrodes at a constant speed (thread speed 100 m / min,
(Range ± 12.5%, chart speed 10 cm / min), the change in electric capacity proportional to the change in cross section was continuously measured, and the average deviation coefficient "U%" of the constant length of the yarn was measured.

Number of fluffs generated in polyester fiber
Number : The fluff existing in a yarn length of 10 ⁷ m or more was detected by a fluff sensor manufactured by Sun Denshi Kogyo Co., Ltd., and converted into the number of fluffs per 10 ⁶ m of the yarn length and displayed.

Example 1 (1) Polyethylene terephthalate (Intrinsic viscosity [η]
= 0.65) 1.0 part by weight of titanium oxide having an average particle size of 0.4 μm was added to 100 parts by weight, melt-mixed using a twin-screw extruder, extruded in a strand shape, and cut to form titanium oxide. Pellets of polyethylene terephthalate containing 1.0% by weight were produced. (2) Using the polyethylene terephthalate pellet containing titanium oxide obtained in (1) above, the number of holes is 4
From eight spinnerets (diameter of spinning holes = 0.2 mm), melt spinning was performed under the conditions of a spinning temperature of 290 ° C. and a spinning rate of 1.02 g / min per hole. A 1.0 m long horizontal blowing type cooling air blowing device was installed immediately below the spinneret, and the polyester fibers spun from the spinneret were immediately introduced into the cooling air blowing device, and the temperature was 25 ° C and the humidity was 65 RH%. The cooled air adjusted to 2 was blown onto the spun fiber at a speed of 0.5 m / sec to cool the fiber to 80 ° C. or lower (temperature of fiber at outlet of cooling air blowing device = 65 ° C.).

(3) A polyester heater having a length of 1.0 m and an inner diameter of 30 mm in which the polyester fiber cooled to 80 ° C. or lower in the above (2) is installed at a position 1.5 mm from directly below the spinneret (inner wall temperature 170 ° C.) After being introduced into the pipe heater and drawn in the pipe heater, an oil agent is applied to the fibers coming out of the pipe heater by a guide oily method, and subsequently a pair of (2
The individual polyester fibers were wound at a take-up speed of 4500 m / min via a take-up roller to produce a stretched polyester fiber. (4) The spinnability of the polyester fiber when the spinning / drawing steps (2) to (3) are performed, and the strength, elongation, and uniformity (Worcester spot: U%) of the finally obtained polyester fiber. ) And the number of generated fluff were measured or evaluated by the above-mentioned method, and were as shown in Table 2 below.

Example 2 A polyester fiber was produced in the same manner as in Example 1 except that the amount of titanium oxide added to polyethylene terephthalate was changed to 3.0% by weight, and the spinnability at that time and finally The strength, the elongation, the uniformity (Worcester spots: U%) and the number of generated fluffs of the obtained polyester fiber were measured or evaluated by the above-mentioned methods, and the results are shown in Table 2 below.

Example 3 Titanium oxide having an average particle size of 1.0 μm was used in place of the titanium oxide used in Example 1, and the amount of titanium oxide added to polyethylene terephthalate was 4.0% by weight. A polyester fiber was produced in the same manner as in Example 1 except that the polyester fiber was spun at that time, and the strength, elongation, uniformity (Worcester spot: U%) and fluff of the finally obtained polyester fiber. Was measured or evaluated by the above method,
The results are shown in Table 2 below.

Examples 4 to 5 Instead of the titanium oxide used in Example 1, silica having an average particle size of 0.03 μm was used, and the amount of silica added to polyethylene terephthalate was 1.0% by weight, respectively. A polyester fiber was produced in the same manner as in Example 1 except that (Example 4) and 5.0% by weight (Example 5) were used, and the spinnability at that time and the strength of the polyester fiber finally obtained. ,
The elongation, uniformity (Worcester spots: U%), and the number of fluffs generated were measured or evaluated by the methods described above, and the results are shown in Table 2 below.

Example 6 Instead of the titanium oxide used in Example 1, silica having an average particle size of 0.4 μm was used, and the amount of silica added to polyethylene terephthalate was 10.0% by weight. Produced polyester fiber in the same manner as in Example 1, and the spinnability at that time was measured.
Also, the strength, elongation, uniformity (Worcester spots: U%) and the number of fluffs generated in the finally obtained polyester fiber were measured or evaluated by the above-mentioned methods, and the results are shown in Table 2 below. .

Example 7 Barium sulfate having an average particle size of 0.6 μm was used in place of the titanium oxide used in Example 1, and the addition amount of barium sulfate to polyethylene terephthalate was 5.0% by weight. A polyester fiber was produced in the same manner as in Example 1 except that the polyester fiber was spun at that time, and the strength, elongation, uniformity (Worcester spot: U%) and fluff of the finally obtained polyester fiber. The number of occurrences of the above was measured or evaluated by the above-mentioned method and was as shown in Table 2 below.

Comparative Example 1 A polyester fiber was produced in the same manner as in Example 1 except that polyethylene terephthalate to which no titanium oxide was added was used, and the spinnability at that time and the polyester finally obtained. When the strength, elongation, uniformity (Worcester spot: U%) of fibers and the number of fluff generated were measured or evaluated by the above-mentioned methods,
The results are shown in Table 2 below.

Comparative Example 2 Polyester fibers were produced in the same manner as in Example 1 except that the amount of titanium oxide added to polyethylene terephthalate was changed to 0.05% by weight, and the spinnability at that time and finally Strength, elongation and uniformity of the obtained polyester fiber (Worcester spot: U%)
The number of fluffs generated and the number of fluffs generated were measured or evaluated by the methods described above, and the results are shown in Table 2 below.

Comparative Example 3 A polyester fiber was produced in the same manner as in Example 1 except that the amount of titanium oxide added to polyethylene terephthalate was changed to 15.0% by weight, and the spinnability at that time and finally Strength, elongation and uniformity of the obtained polyester fiber (Worcester spot: U%)
The number of fluffs generated and the number of fluffs generated were measured or evaluated by the methods described above, and the results are shown in Table 2 below.

Comparative Example 4 Titanium oxide having an average particle size of 2.0 μm was used in place of the titanium oxide used in Example 1, and the amount of titanium oxide added to polyethylene terephthalate was 3.0% by weight. A polyester fiber was produced in the same manner as in Example 1 except that the polyester fiber was spun at that time, and the strength, elongation, uniformity (Worcester spot: U%) and fluff of the finally obtained polyester fiber. Was measured or evaluated by the above method,
The results are shown in Table 2 below.

Comparative Example 5 Instead of the titanium oxide used in Example 1, silica having an average particle size of 0.03 μm was used, and the addition amount of the silica to polyethylene terephthalate was changed to 0.05% by weight. Example 1 except for
Polyester fiber is produced in the same manner as above, and the spinnability at that time and the strength, elongation, uniformity (Worcester spot: U%) of the finally obtained polyester fiber and the number of fluff generated are as described above. Upon measurement or evaluation, it was as shown in Table 2 below.

Comparative Example 6 Instead of the titanium oxide used in Example 1, silica having an average particle size of 0.03 μm was used, and the addition amount of the silica to polyethylene terephthalate was changed to 15.0% by weight. Example 1 except for
Polyester fiber is produced in the same manner as above, and the spinnability at that time and the strength, elongation, uniformity (Worcester spot: U%) of the finally obtained polyester fiber and the number of fluff generated are as described above. Upon measurement or evaluation, it was as shown in Table 2 below.

[0042]

[Table 2]

From the results shown in Table 2 above, the average particle size was 0.0
In the case of Examples 1 to 7 in which direct spinning and drawing is carried out by the above-mentioned method of the present invention using polyester containing 1 to 1.0 μm of inorganic fine particles in a proportion of 0.1 to 10% by weight, Excellent strength and elongation, and Worcester spot (U value)
It can be seen that the high-quality drawn polyester fiber having a low value, excellent in uniformity and, at the same time, little or no fluff generation can be smoothly produced with extremely good spinnability without causing yarn breakage.

On the other hand, Comparative Example 1 using polyethylene terephthalate containing no inorganic fine particles,
Even if the inorganic fine particles having an average particle diameter of 0.01 to 1.0 μm are contained, the content thereof is within the above range (0.
In the cases of Comparative Examples 2 to 3 and Comparative Examples 5 to 6 which are out of the range of 1 to 10% by weight), the resulting stretched polyester fibers have large Worcester spots (U value) and are non-uniform, and moreover fluff is generated. The stretched polyester fiber is significantly higher than the examples, and the quality of the finally obtained stretched polyester fiber is significantly inferior to the examples, and the spinnability is also poor and the stretched polyester has good process stability. It turns out that no fibers can be obtained.

Further, the average particle size of the inorganic fine particles is 2.0 μm.
Also in the case of Comparative Example 4 in which the average particle size of the inorganic fine particles used in the present invention is out of the range, Worcester spots (U value) of the obtained stretched polyester fiber are large and non-uniform, and fluff is generated. Is significantly higher than that of the examples, and the quality of the obtained stretched polyester fibers is significantly inferior to that of the examples. Furthermore, the spinnability is also poor and the stretched polyester fibers are obtained with good process stability. It turns out that you can't.

[0046]

According to the method of the present invention, high-quality polyester fiber free from fluff generation and thickness unevenness, and excellent in mechanical properties such as strength and elongation is used. It can be produced with good productivity by a direct spin-drawing method with good processability.

Claims (1)

[Claims] 1. A fiber-forming polyester containing 0.1 to 10% by weight of inorganic fine particles having an average particle diameter of 0.01 to 1.0 μm is melt-spun and then cooled to a temperature below its glass transition temperature. Then, the polyester fiber is introduced into the heating zone, drawn, and then taken off at a speed of 3500 m / min or more.