JP7332307B2 - Method for producing highly hollow polyester fiber - Google Patents

Description

The present invention relates to a method for producing highly hollow polyester fibers.

Many of the conventionally proposed highly hollow polyester fibers having a hollowness of 40% or more use a special spinning method to obtain a highly hollowed state.

Patent Document 1 proposes a method in which a molten polymer is discharged from a nozzle in which a portion surrounded by a plurality of slit holes occupies a large percentage of the circumscribed circle area, and is spun and drawn under normal conditions. However, the lower limit of the slit width is about 0.05 to 0.03 mm. Since the minimum discharge rate per discharge hole increases and the fineness increases, it is difficult to obtain a highly hollow polyester fiber with a fine fineness and a hollow ratio of 40% or more, and the actual situation is that it is manufactured under limited spinning conditions. be.

Patent Document 2 proposes a method of introducing an inert gas such as nitrogen gas from the inside of a slit-shaped nozzle to cool the discharged yarn from the inside and outside. According to this method, highly hollow polyester fibers can be obtained, but the number of holes cannot be increased due to the complicated structure of the nozzle. Therefore, there is a drawback that the production capacity is extremely lowered to obtain a fine fineness, resulting in an increase in cost.

In Patent Documents 3 and 4, when a molten polyester is extruded from a spinneret having a known hollow fiber manufacturing spinning hole composed of a plurality of slits to obtain a hollow undrawn yarn, the extruded yarn is rapidly cooled immediately below the spinneret, then slowly cooled, and spun at a spinning draft of 150 or more and a take-up speed of 1000 to 1800 m / min. A fiber with a fineness of 0.1 to 8.0 denier (9.0 decitex) and a high hollowness of 40 to 85% is obtained by drawing (neck drawing) at a draw ratio of 8 to 5.5 times. A method is disclosed. However, due to rapid cooling directly below the spinneret and high spinning draft to obtain a high hollow ratio, the molten polyester solidifies before joining, causing cracks on the surface of the hollow fibers (called hollow breakage), There are drawbacks such as breakage (also called broken yarn) and broken yarn during drawing due to hollow breakage of undrawn yarn.

Therefore, the actual situation is that the above-mentioned prior art cannot stably produce highly hollow polyester fibers while maintaining high productivity.

JP-A-6-2210 JP-A-62-289642 JP-A-11-302921 JP-A-10-292222

The present invention was made against the background of the above-mentioned prior art, and its object is to break spun yarn by hollow breakage in the manufacturing process of polyester fibers with a high hollow ratio of 40% or more in the cross section of the fiber. To provide a stable production method that suppresses stretched yarn and broken yarn.

As a result of intensive studies to solve the above problems, the present inventors have found a production method that stabilizes the process condition of spinning and drawing by suppressing the hollowness of undrawn yarn and making it highly hollow by drawing. The discovery led to the completion of the present invention.

That is, according to the present invention,
1. A method for producing a highly hollow polyester fiber characterized by flow-drawing hollow polyester undrawn fibers having a hollowness of 15 to 35% so that the hollowness of the fibers after stretching is 40 to 90%,
As another invention, 2. The high hollow fiber obtained by the method described in 1 above is further neck-drawn to achieve both a fine fineness and a high strength, and has a single fiber fineness of 0.1 to 9.0 dtex and a tensile strength. is 2 cN/dtex or more.

According to the production method of the present invention, a polyester fiber having a high hollowness of 40 to 90% is obtained from a hollow undrawn fiber having a hollowness of 15 to 35%. , both spun yarn breakage and drawn yarn breakage are reduced, and a high yield can be achieved.

1 is a cross-sectional view of a high hollowness fiber of the present invention; FIG. It is an example of the shape of the discharge hole used to obtain the undrawn yarn of the present invention. It is an example of the shape of a discharge hole used for obtaining a high hollowness fiber of the prior art (Patent Document 1).

The present invention will be described in detail below.
The polyester fiber of the present invention is an ethylene terephthalate-based homopolyester or copolyester having ethylene terephthalate as a main repeating unit, or a polyester obtained by mixing these polyesters with a third component, and particularly 90 mol % or more of the repeating unit. are ethylene terephthalate units, and homopolyethylene terephthalate is most preferred.

Examples of copolymerizable components that can be copolymerized at 10 mol % or less include aromatic dicarboxylic acids such as isophthalic acid, 5-sodiumsulfoisophthalic acid, diphenyldicarboxylic acid and naphthalenedicarboxylic acid as acid components, oxalic acid, adipic acid, and sebacic acid. , dodecanedioic acid and other aliphatic dicarboxylic acids, p-oxybenzoic acid, P-β-hydroxyethoxybenzoic acid and other oxycarboxylic acids. -aliphatic diols such as butanediol, 1,6-hexanediol and neopentyl glycol; aromatic diols such as 1,4-bis(β-hydroxyethoxy)benzene; polyalkylenes such as polyethylene glycol and polytetramethylene glycol; Glycol and the like can be mentioned. These third components may be copolymerized singly or two or more of them may be copolymerized simultaneously.

The degree of polymerization (intrinsic viscosity) of the polyester does not have to be particularly limited, but if it is too large, the process stability during spinning tends to decrease, making it difficult to obtain fine fineness, while if it is too small, it will be highly hollow. Therefore, the intrinsic viscosity IV measured in orthochlorophenol at 35° C. is in the range of 0.45 to 1.00, preferably 0.5 to 0.9.

In addition, the above polyester may be mixed with various additives, such as antibacterial agents, hydrophilic agents, anti-mite agents, deodorants, various function-imparting agents such as far-infrared radiation agents, titanium dioxide, silicon oxide, oxidation Inorganic fine particles such as zinc, barium sulfate, zirconium oxide, aluminum oxide, magnesium oxide, calcium oxide, and tourmaline can be mentioned, and can be appropriately selected and used depending on the purpose. However, when blending inorganic fine particles, the average particle size is 1.0 μm or less, preferably 0.1 to 0.7 μm, from the viewpoint of dispersibility in polyester. A suitable amount is 1 to 10% by weight, particularly 2 to 7% by weight.

Hollow polyester undrawn fibers can be collected using the same process and spinneret as known hollow polyester undrawn fibers, and can be highly hollowed by applying flow drawing described later. Well, unlike the prior art, high hollowness is not required after polymer extrusion, so it is possible to reduce spun yarn breakage, hollow breakage, and accompanying drawn yarn breakage. FIG. 2 shows an example of the hole shape of a known hollow spinneret used. If the hollow ratio is less than 15%, it is difficult to increase the hollow ratio to 40% or more even after flow drawing. . The preferred range of hollowness for hollow polyester undrawn fibers is 18-33%.

In addition, the hollow polyester undrawn fibers preferably have a spinning speed and a spinning draft as low as possible in order to increase the flow draw ratio and neck draw ratio described later, and the spinning speed is 800 m / min or less, preferably 700 m / min or less. , more preferably 600 m/min or less, and a spinning draft of 140 or less, preferably 120 or less, more preferably 100 or less.

Here, the flow drawing referred to in the present application is a drawing method performed at a temperature higher than the glass transition temperature of polyester under a low tension of 0.1 cN/dtex or less, and the molecular orientation in the undrawn yarn is hardly changed. It is a stretching method that enables high-ratio stretching.

And neck stretching means that at a temperature below the glass transition temperature of polyester, at a tension above the yield stress of the undrawn yarn, and above the natural draw ratio of the undrawn yarn (the length of the constant stress elongation region of the stretching curve of the undrawn yarn Defined by adding +1 to the value divided by the test length, also called NDR), and drawing until the thickness of the undrawn yarn becomes uniform (until the neck point disappears).

A highly hollow polyester is obtained by flow-drawing the above hollow undrawn polyester yarn. In the flow drawing, in the case of polyester, a low drawing of 0.01 to 0.10 cN/dtex, preferably 0.02 to 0.08 cN/dtex is usually performed in a heat medium bath at 70 to 100°C, preferably 75 to 99°C. Since the yarn is drawn under tension, the yarn can be drawn with the molecular orientation almost equal to that of the undrawn yarn, in contrast to the neck drawing in which the molecules are highly oriented in the drawing direction at a drawing tension higher than the yield stress. Therefore, flow drawing under a low tension has the effect of expanding the air trapped in the hollow portions of the undrawn yarn and making the hollow ratio greater than that of the undrawn yarn.

In addition, since flow drawing can make the draw ratio larger than that of neck drawing without causing a large change in molecular orientation, it is possible to reduce the fineness without lowering the elongation. The draw ratio of flow drawing is preferably 5 times or more, more preferably 10 times or more, and still more preferably 15 times or more.

In addition, the fiber after the flow drawing is subjected to neck drawing in a warm water bath at 55° C. to 75° C. at a rate of 1.05 times or more, preferably 1.5 to 5 times, thereby further reducing the fineness and tensile strength. Strength can be improved. The hollowness after neck stretching is almost the same as that after flow stretching.

The highly hollow polyester fiber of the present invention should have a single fiber fineness of 0.1 to 9.0 dtex, preferably 0.2 to 3.0 dtex, particularly preferably 0.6 to 1.7 dtex. be. It is possible to stably produce even if the single fiber fineness is less than 0.1 dtex, but it is necessary to increase the flow drawing ratio considerably, so we think that it is close to the lower limit.

Next, the highly hollow polyester fiber of the present invention must have a hollowness of 40 to 90%, preferably 45 to 85%, more preferably 50 to 80% in the fiber cross section.

If the hollowness ratio is less than 40%, the improvement effect of excellent feeling (drape, flexibility, soft touch), hiding property, bulkiness, heat retention and heat insulation, etc. obtained by hollowing the fiber becomes insufficient. . On the other hand, if it exceeds 90%, the thickness of the wall surface of the hollow becomes too thin, and hollow breakage tends to occur, and the resistance to compressive stress is lowered, resulting in poor shape retention.

If the hollowness of the raw yarn (before stretching) is lower than 15%, a high hollowness of 40% or more cannot be obtained, so the raw yarn must have a hollowness of 15% or more. Here, the hollow ratio means the ratio (%) of the total area of the hollow portion to the area of FIG. 1 surrounded by the outer peripheral portion of the cross section of the fiber.

The number of hollow parts in the cross section of the fiber may be one or more, but in the case of more than one, it becomes difficult to obtain a fiber with a high hollow ratio and a small single fiber fineness. , more preferably one hollow portion.

The shape of the hollow portion is arbitrary, but when it is a perfect circle, it is easy to obtain a high hollow ratio, and it is easy to obtain a shape with advanced orientation in the circumferential direction, so that the recovery characteristics of the hollow shape are good. Therefore, it is preferable.

Regarding the tensile strength, after increasing the hollowness of the raw fiber by flow drawing, by neck drawing as described above, the tensile strength is 2 cN / dtex or more, which is a practical tensile strength for use in various textile products. becomes possible. It is preferably 2.5 cN/dtex, more preferably 3.0 cN/dtex. In addition, the higher the neck draw ratio is compared to the natural draw ratio (NDR), the higher the tensile strength can be obtained.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples. In addition, the measurement of each characteristic value in the examples was carried out according to the following method.
<Fineness>
Measured according to JIS L1015:2010 8.5.1 A method.
<Apparent (appearance) fineness>
Using an image analysis system, Pierce-2 (manufactured by Pierce Co., Ltd.), the cross-sectional image of the single fiber section is magnified 500 times to obtain the cross-sectional area (including the hollow portion), and the specific gravity d of the polymer is 1.38. Calculated assuming
<Hollowness rate>
The cross-sectional area A of the single fiber (the inner area of the outer periphery including the hollow portion) and the hollow portion area B were measured from the above 500-fold cross-sectional image, and the area ratio was determined.
Hollow ratio = B/A x 100 (%)
<Tensile strength>
It was measured according to JIS L1015:2010 8.7.1 method, and the unit was cN/dtex.
<Spinnability and drawability>
Spinnability was evaluated according to the following criteria.
Good (◯): The number of thread breakages is less than 0.05 times/weight/day, the number of adherent threads is less than 0.1/weight/day, and the section variation rate V is less than 8%.
Somewhat poor (Δ): The number of thread breakage is 0.05 to 0.10 times/weight/day, the adherent thread is 0.1 to 0.2/weight/day, and the section variation rate V is 8 to 9%.
Poor (x): The number of yarn breakages exceeds 0.15 times/weight/day, the number of adherent yarns exceeds 0.2/weight/day, and the section variation rate V exceeds 9%.
However, the coherent yarn referred to here means one in which two or more single yarns are fused together, and the section variation rate V is obtained by randomly measuring the yarn diameter from a single yarn cross-sectional photograph (n = 20). Shows the variation when
Section variation rate V = standard deviation of thread diameter / average value of thread diameter x 100 (%)
In addition, stretchability was evaluated according to the following criteria.
Good (○): single yarn broken roller winding less than 0.5 times/day, unstretched less than 5/100,000;
Slightly poor (△): 0.5 to 2 times/day of single yarn broken roller winding, 5 to 10/100,000 unstretched,
Defective (x): Single yarn broken roller winding more than 2 times/day, unstretched more than 10/100,000. , refers to a state in which the broken end is wound around the rotating drawing roller and it is difficult to continue drawing as it is in terms of drawn yarn quality and drawing machine maintenance.

[Example 1]
Polyethylene terephthalate containing 0.3% by weight of titanium oxide and having an intrinsic viscosity of 0.64 was extruded from a spinneret having a hollow nozzle with 408 holes shown in FIG. An undrawn yarn having a single fiber fineness of 19.1 dtex and a hollow ratio of 17% was obtained by taking off at a speed of 500 m/min. The cooling conditions below the nozzle at this time were as follows: cooling air blowing position: 48 mm, cooling air blowing length: 200 mm, cooling air temperature: 30°C, cooling air humidity: 70%, cooling air speed: 0.5 m/sec. The obtained hollow undrawn yarn was flow-drawn at a tension of 0.03 cN/dtex in warm water at a temperature of 97°C to 6.9 times, and then neck-drawn at a factor of 2.9 in warm water at a temperature of 75°C. to obtain a polyester fiber. This was crimped with 12 to 13 crimps/25 mm, heat-set with hot air at 140° C., and cut into short fibers having a fiber length of 51 mm.
Table 1 shows the evaluation results of the obtained hollow polyester short fibers.

[Example 2]
It was carried out in the same manner as in Example 1 of the present invention, except that the flow draw ratio was changed to 15.0 times.
Table 1 shows the evaluation results of the obtained hollow polyester short fibers.

[Example 3]
It was carried out in the same manner as in Example 1 of the present invention, except that the drawing conditions were changed to those shown in Table 1 (flow drawing only). Table 1 shows the evaluation results of the obtained hollow polyester short fibers.

[Comparative Example 1]
It was carried out in the same manner as in Example 1 of the present invention, except that the drawing conditions were changed to those shown in Table 1 (only the neck drawing). Table 1 shows the evaluation results of the obtained hollow polyester short fibers .

[ Comparative Example 2 ]
By changing the cooling conditions in the same manner as in Example 1 of the present invention, an undrawn yarn having a single filament fineness of 9.1 dtex and a hollow ratio of 10% was obtained. As in Example 2, the film was stretched 15 times by flow stretching and 2.9 times by neck stretching. Spinnability and drawability were good, but the resulting fiber had a hollowness of 26%, and a high hollowness fiber with a hollowness of 40% or more could not be obtained. Table 1 shows the evaluation results of the obtained hollow polyester short fibers.

According to the present invention, it is possible to improve the quality and yield of highly hollow fibers having a hollowness of 40% or more compared with the prior art. The obtained high hollow fiber has excellent functions such as light weight, heat retention, bulkiness, shape retention, and wrinkle resistance, and is suitable for woven and knitted fabrics, nonwoven fabrics, batting for clothing, bedding, fiber structures, etc. Used.

a: high hollow fiber b: hollow portion c: slit hole (slit nozzle)
d: protrusion

Claims (4)

A method for producing a highly hollow polyester fiber, comprising flow-drawing an undrawn hollow polyester fiber having a hollowness of 15 to 35% so that the hollowness of the fiber after stretching is 40 to 90%. The method for producing a highly hollow polyester fiber according to claim 1, wherein the flow drawing is performed in a hot water bath at 70 to 100°C at a low tension of 0.01 to 0.10 cN/dtex. 3. The method for producing a highly hollow polyester fiber according to claim 1 or 2, wherein, after the flow drawing, neck drawing is performed under conditions involving molecular orientation by subsequently applying a tension equal to or higher than the yield stress. The method for producing a highly hollow polyester fiber according to claim 3, wherein the highly hollow polyester fiber obtained by the above method has a single fiber fineness of 0.1 to 9.0 dtex and a tensile strength of 2 cN/dtex or more. A method for producing highly hollow polyester fibers.

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