JPH10251933A - Production of heat-expandable polyester staple - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a heat-stretchable polyester staple, by which the staple having high heat stretchability is produced at a low cost and in a good productivity. SOLUTION: This method for producing a heat-stretchable polyester staple by using a polyester undrawn fiber bundle wound at <=2,500m/min winding rate comprises a step for drawing the undrawn fiber bundle comprising undrawn fiber containing >=1wt.% metal oxide and having 3-6 leaves cross section at a temperature from (Tg-10 deg.C) to (Tg+30 deg.C) [Tg is a glass transition temperature ( deg.C) of the undrawn fiber] at a draw ratio from the natural draw ratio to 1.2 times as many as the natural draw ratio, a step for successively carrying out a heat treatment of the drawn fiber bundle relaxed in not less than 5% at a temperature from (Tg+30 deg.C) to (Tg+120 deg.C), a step for providing crimps to the heat treated fiber bundle and imparting a finishing oiling agent, and a step for drying and cutting the fiber bundle with crimps and the finishing oiling agent at a temperature not higher than the Tg.

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 heat-extensible polyester short fiber which has the property of being stretched by heating, and can be used as a spun yarn to produce a fabric having a soft feeling when knitted and woven. Things.

[0002]

2. Description of the Related Art Polyester fibers represented by polyethylene terephthalate are widely used for clothing, industrial materials and the like. Polyester fibers have properties of high orientation and high crystallinity, and thus have excellent properties such as firmness and stiffness, but have a drawback that softness typified by softness is slightly inferior. In order to impart softness to a fabric, a method of using a polyester fiber that is elongated by heat treatment is known, and various types of such heat-extensible polyester fibers have been proposed, including a method for producing the same.

[0003] Japanese Patent Application Laid-Open No. 3-139948 discloses a method of producing a heat-extensible polyester fiber by heat-treating a polyester highly oriented undrawn yarn under low tension and then drawing it at a low draw ratio. However, in order to obtain a highly oriented undrawn yarn, it is necessary to perform high-speed spinning at about 3000 m / min or more. Therefore, in the case of producing short fibers, the spinnability deteriorates, and the spinning machine base is further limited. There is a problem that the productivity is poor and the cost is higher than using low-oriented undrawn yarn.

Japanese Patent Application Laid-Open No. Hei 7-11513 discloses a birefringence (△
A method is disclosed in which a low-oriented undrawn yarn having n) of 0.008 or less is heat-treated at Tg to 180 ° C, then drawn at a drawing temperature of 80 to 120 ° C and a draw ratio of 2.2 to 2.7 times, and subjected to relaxation heat treatment at Tg or less. . However, in order to develop heat extensibility using a low-oriented undrawn yarn, it is necessary to perform heat treatment for a longer time than when using a highly-oriented undrawn yarn, and the operability is poor.

[0005] In order to solve such a problem, the present inventors disclosed in Japanese Patent Application No. 7-344458 a method in which a polyester low-orientation unstretched yarn bundle was cut at a low tension and a draw ratio of the unstretched yarn bundle.
After stretching under the conditions of a stretching ratio of 80% or more and a stretching temperature of Tg + 20 ° C or more, a continuous heat treatment is performed and dried at Tg or less to obtain a heat-extensible fiber in a relatively short time. A method was proposed. By using this method, the heat treatment time can be considerably shortened.However, in the drawing step, since the fiber is uniformly deformed and drawn, the fiber may be slightly fused, and the heat extensibility of the obtained fiber may be reduced. I couldn't make it that big.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and by using a specific polyester low-orientation undrawn yarn, a short fiber having a sufficient heat extensibility can be produced in a short time with high productivity. An object of the present invention is to provide a method for producing a heat-extensible polyester short fiber which can be produced.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have reached the present invention. That is, the present invention is a method for producing a heat-extensible polyester short fiber using a polyester undrawn yarn bundle wound at a winding speed of 2500 m / min or less, comprising 1% by weight or more of a metal oxide, An unstretched yarn bundle consisting of unstretched yarns having three to six leaf cross-sections is stretched at a temperature of Tg−10 to Tg + 30 ° C. at a stretch ratio of the natural stretch ratio of the unstretched yarn to the natural stretch ratio × 1.2 and continuously. 5% at a temperature of Tg + 30 to Tg + 120 ° C
The above-described relaxation heat treatment is performed, and then, the yarn bundle is crimped, a finishing oil agent is applied thereto, and then dried at a temperature of Tg or less, and cut. Is what you do. However, Tg: glass transition temperature of undrawn yarn (° C)

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. First, the polyester used in the present invention has ethylene terephthalate as a main repeating unit. However, in order to give a change in dyeing properties and feeling, if it is about 5 mol% or less, isophthalic acid, 5 -Aromatic dicarboxylic acids such as sodium sulfoisophthalic acid,
Copolymerization of aliphatic dicarboxylic acids such as adipic acid and sebacic acid, aliphatic diols such as 1,4-butanediol and 1,6-hexanediol as alcohol components, and aromatic diol components such as ethylene oxide adducts of bisphenols. May be done. Further, an antioxidant, an ultraviolet absorber, a stabilizer, a fluorescent whitening agent, a pigment and the like may be added.

The unstretched polyester yarn bundle used in the present invention is wound at a winding speed of 2500 m / min or less, contains 1% by weight or more of metal oxide, and is composed of an unstretched yarn having a cross section of three to six leaves. is there.

In the present invention, in order to obtain an unstretched yarn bundle at a low cost without using a special machine, the polyester unstretched yarn bundle wound at a winding speed of 2500 m / min or less is used in the present invention. Used. As the lower limit of the winding speed, if the winding speed is too low, undrawn yarn with extremely low orientation is obtained, and the yarn is easily cut at the time of drawing. Therefore, the lower limit is preferably about 500 m / min.

Further, the undrawn yarn is made up of 1% by weight of metal oxide.
By containing the above, by having a cross-sectional shape of three to six leaves,
The orientation of the undrawn yarn obtained by the low-speed spinning is advanced to some extent, and in a subsequent drawing and relaxation heat treatment step, a fiber having sufficient heat extensibility can be obtained in a short time. That is, since the undrawn yarn contains the metal oxide in an amount of 1% by weight or more, the metal oxide serves as a nucleating agent and crystallization is accelerated, and the yarn extruded from the nozzle in the spinning process is rapidly cooled. Since the orientation of the undrawn yarn proceeds, it is possible to obtain a highly oriented yarn to some extent.

When the amount of the metal oxide is less than 1% by weight,
As described above, since the orientation of the undrawn yarn does not progress, in the drawing and relaxation heat treatment steps, it may take a long time to impart heat extensibility, or it may be sufficient heat extensibility. Can not. The upper limit of the amount of the metal oxide is not particularly limited, but if the content of the metal oxide is too large, the metal oxide is clogged in the filter agent layer in the spinneret pack during spinning, and the spinning operability is reduced. It is preferable to set the content to about 5% by weight because of deterioration.

Examples of the metal oxide include oxides such as Ti, Si, Al, and Fe. Among them, TiO ₂ and talc are preferably used. The particle diameter of the metal oxide is 1 μm
m or less is preferred. If the particle size is too large, the metal oxide is clogged in the filter agent layer in the spinneret pack during spinning, as in the case where too much metal oxide is added, and the spinning operability deteriorates.

Further, it is necessary to make the cross-sectional shape of the undrawn yarn three to six leaves. However, by making the cross-sectional shape of the undrawn yarn three to six leaves, the surface area becomes larger than that of the round cross section.
In the same manner as described above, the orientation of the undrawn yarn proceeds by increasing the cooling rate of the yarn, and the yarn becomes highly oriented to some extent. Thereby, in a later step, a fiber having sufficient heat extensibility can be obtained in a short time. When the cross-sectional shape exceeds six leaves, the surface area of the yarn is almost the same as the round cross-section,
The cooling rate cannot be increased, and a highly oriented yarn cannot be obtained.

Next, the undrawn yarn bundle is subjected to a temperature Tg-10 to Tg +
At 30 ° C., the natural drawing ratio of the undrawn yarn to the natural drawing ratio ×
Stretch at a stretch ratio of 1.2. As described above, by stretching at a relatively low temperature and at a low magnification, necking stretching is performed, and the fusion of fibers does not occur as compared with the uniform stretching in which uniform deformation is performed.

If the drawing temperature is lower than Tg-10 ° C., the molecular flow inside the fiber is not promoted, and the drawing cannot be performed sufficiently, so that the fiber breaks at the time of drawing or the fiber becomes thick and thin. On the other hand, if the temperature exceeds Tg + 30 ° C, necking stretching is not performed, and uniform stretching is performed. In some cases, fiber fusion or thread breakage occurs, and the fiber does not have sufficient heat extensibility. The resulting woven or knitted fabric has poor softness.

If the stretching ratio is less than the natural stretching ratio (hereinafter, referred to as NDR) of the undrawn yarn bundle, the undrawn portion remains, causing staining spots and yarn breakage in post-processing. And it cannot be a heat-extensible fiber. Meanwhile, NDR
If it exceeds 1.2, the structure of the fiber becomes stable at the time of drawing, and it cannot be a heat-extensible fiber.

Such stretching may be carried out by changing the speed between the rollers, and the stretching may be performed by setting the temperature using the rollers as heating rollers.

Tg + 30 to Tg + 12
Perform a relaxation heat treatment of 5% or more at a temperature of 0 ° C. If the relaxation heat treatment temperature is lower than Tg + 30 ° C., the yarn bundle is not sufficiently heat-treated, and thus cannot be made into a heat-extensible fiber.
On the other hand, if it exceeds Tg + 120 ° C, the heat treatment temperature is too high,
Since the internal structure of the fiber is fixed, the fiber cannot be a heat-extensible fiber.

Further, the relaxation rate during the relaxation heat treatment needs to be 5% or more. If the relaxation rate is less than 5%, the fibers are not sufficiently relaxed and do not become heat extensible fibers. The upper limit of the relaxation rate is not particularly limited, but if it is too high, troubles such as yarn breakage occur in the drawing process, and fluff and loops frequently occur in the spinning process, and the permeability in the weaving and weaving process is reduced. Since it becomes a bad fiber, it is preferable to set it to about 30%.

The relaxation heat treatment is preferably performed by using a non-contact heat treatment heater. When producing short fibers, since the fibers are supplied to the heat treatment step in the state of bundled yarns, it may be difficult to perform uniform heat treatment on the yarn bundles when using a contact heat treatment heater, and the yarn quality performance may vary. Tends to occur. Examples of the non-contact heat treatment heater include a heater that performs heat treatment by blowing heated steam or irradiating microwaves.

When the relaxation heat treatment is performed using such a non-contact type heat treatment heater, the heat treatment time is short, and
The time is preferably 10 seconds, more preferably 1 to 7 seconds.
If the heat treatment time exceeds 10 seconds, the fiber shrinks excessively or the internal structure of the fiber is stabilized, and if the heat treatment time is less than 1 second, the heat treatment is insufficient and the yarn bundle is sufficiently Since they do not shrink, they do not become heat extensible fibers in any case.

Further, the drawn and relaxed heat-treated yarn bundle is crimped and a finishing oil is applied, dried at a temperature of Tg or less, and cut into short fibers. The means for imparting crimp is not particularly limited, and a method of imparting the material by a press-type crimper can be employed. The number of crimps and the fiber length may be appropriately selected according to the application, but when used as a spun yarn, the number of crimps is 10 to 30/25.
mm is preferable. In addition, as the finishing oil, anionic surfactants, nonionic surfactants, those appropriately mixed depending on the application and the like are used,
Examples of a method of applying the method include a method of immersing the yarn bundle in a liquid tank and spraying the yarn bundle on the yarn tank.

When dried at a temperature exceeding Tg,
The fiber elongates, and becomes a fiber that does not exhibit extensibility by the treatment in the subsequent step. The fiber length for cutting the yarn bundle is preferably about 30 to 100 mm.

According to the production method of the present invention, specifically, heat extensible short fibers having a boiling water elongation of about 3.0 to 6.0% and a dry heat elongation of about 7.0 to 10.0% can be obtained.

As described above, three to three metal oxides
By using an undrawn yarn having a six-leaf cross-section, the metal oxide acts as a nucleating agent, and the surface area of the yarn increases, and the cooling speed of the yarn increases, so that the winding speed is 2500 m / min or less. Although it is a polyester undrawn yarn that was taken,
An undrawn yarn having a certain degree of orientation can be obtained. By using such a yarn bundle made of an undrawn yarn, drawing, relaxation heat treatment, and the like are performed under the above conditions, without causing fusion to the fiber, and excellent in a short heat treatment. A heat extensible polyester short fiber can be obtained. As described above, the heat-extensible staple fiber obtained in the present invention is an excellent heat-extensible fiber. When applied, the fibers elongate, and a soft and soft-textured fabric can be obtained. Further, when the short fiber and the heat-shrinkable fiber obtained in the present invention are mixed and spun into a spun yarn, the fabric obtained by knitting and weaving is heat-shrinkable by a post-treatment such as dyeing. Excellent bulkiness due to the effect of fiber,
It has a soft and flexible feel.

Next, the manufacturing method of the present invention will be described with reference to the drawings. FIG. 1 is a schematic process diagram of a stretching step and a relaxation heat treatment step showing one embodiment of the production method of the present invention. First, speed
Unstretched yarn having a cross section of 3 to 6 leaves containing 1% by weight or more of metal oxide, wound at 2500 m / min or less
After the yarn bundle Y is stretched between the first roller group 1 (heat roller) and the second roller group 2, the non-contact heat treatment heater 3 is used. Then, it is subjected to relaxation heat treatment, and is taken up by the take-up roller group 4. At this time, the speed of the take-off roller group 4 is set to be lower than the speed of the second roller group 2 so as to change the relaxation rate. Next, crimping is performed by a press-in type crimper or the like, and a finishing oil is applied, followed by drying with a drier and cutting of the thread bundle with a cutter.

[0028]

Next, the present invention will be described in detail with reference to examples. The characteristic values in the examples were measured as described below. (1) Intrinsic viscosity [η] Measured at 20 ° C. using an equal weight mixture of phenol and ethane tetrachloride as a solvent. (2) Tg, Tm (melting point) of undrawn yarn Using a differential scanning calorimeter DSC-7 manufactured by PerkinElmer,
The measurement was performed at a heating rate of 10 ° C./min. (3) Using the undrawn yarn NDR Orientic Tensilon UTM-4-100,
At an elongation rate of 10 cm / min, draw a strong elongation curve of the undrawn yarn (sample length 10 cm) constituting the undrawn yarn bundle, and naturally stretch elongation (En) in a region where necking proceeds and elongation is performed at a constant stress.
Was calculated, and the natural draw ratio (NDR) was calculated by the following equation. NDR = (En + 100) / 100 (4) Elongation ratio of boiling water (E100) The sample was treated in boiling water for 30 minutes without load, and the length before the treatment (R ₀ ) and the length after the treatment (R ₁ ) From the following equation, it was calculated. The load at the time of measurement was 1/30 g / denier. Boiling water elongation (E100) (%) = [(R ₁ -R ₀₎ /
R ₀ ] × 100 (5) Dry heat elongation (160 ° C.) The sample was treated in a high-temperature atmosphere of 160 ° C. for 30 minutes without load, and the length before and after the treatment was measured and calculated in the same manner as above. . (6) Hand feeling (soft feeling) The obtained heat-extensible short fiber was used as a spun yarn having a yarn count of 50, and
Weave a plain woven fabric of book / 2.54 cm, weft 33 / 2.54 cm,
After applying a finishing heat treatment at 180 ° C for 15 minutes and dyeing it under the following conditions, the texture (soft feeling) of the fabric is scored by a 10 panelist with a touch of 10 points, and the total score is calculated. Was evaluated. 80 points or more Very soft 60-79 points Soft 40-59 points Slightly hard 39 points or less Hard dye: Resoline Blue GRL (Bayer disperse dye)
1% owf auxiliary agent: Disper VG (manufactured by Meisei Chemical Co., Ltd.) 2% owf bath ratio: 1:50, dyeing temperature × time: 100 ° C. × 1 hour

Examples 1 to 6 and Comparative Examples 1 to 6 [η] 0.70, Tg 71 ° C., Tm 256 ° C. Polyethylene terephthalate was spun at a spinning temperature of 295 ° C. using an ordinary spinning apparatus.
At a winding speed of 1100 m / min. At this time, TiO ₂ was used as the metal oxide, and the content was variously changed as shown in Table 1. And spinneret (800 holes)
Is a three-leaf (Examples 1-3, Comparative Example 5), a six-leaf (Examples 4-6, Comparative Example 6), and a round (Comparative Examples 1-4). Obtained. Table 1 shows the NDR of the obtained undrawn yarn. The undrawn yarn was bundled to form a 800,000-denier yarn bundle, and subjected to drawing and relaxation heat treatment using an apparatus shown in the schematic process diagram of FIG. 1 to produce short fibers. At this time, the stretching temperature between the first and second roller groups (the first roller group 1
The stretching was performed at a temperature of 75 ° C. and a stretching ratio of NDR × 1.1. Subsequently, the relaxation heat treatment was performed by passing through a non-contact type heat treatment heater 3 heated by heated steam and taking it by a group of take-off rollers 4. At this time, the relaxation heat treatment temperature (temperature of the heated steam) was 130 ° C., the relaxation rate was 10%, and the treatment was performed for 5 seconds. Next, a crimp of 10 pieces / 25 mm is applied with a press-type crimper, a finishing oil is applied, dried at 60 ° C., cut with a cutter, and cut into short fibers having a fiber length of 5.1 cm (single fiber fineness of 3.5 mm)
d) was obtained. Table 1 shows the evaluation results of the elongation rate of boiling water, the elongation rate of dry heat, and the feeling of the woven fabric obtained from these fibers.
Shown in

[0030]

[Table 1]

As is clear from Table 1, according to Examples 1 to 6, excellent heat-extensible fibers were obtained, and the woven fabric using these fibers had a soft feel. on the other hand,
Comparative Example 1 did not contain TiO ₂ and used an undrawn yarn having a round cross-sectional shape. Comparative Examples 5 and 6 had a trilobal or six-leaf cross-sectional shape but used an undrawn yarn not containing TiO _2. However, the metal oxide did not work as a nucleating agent, and the resulting fiber had poor heat extensibility. In Comparative Examples 2 to 4, the unstretched yarn having a round cross-sectional shape was used, so that the obtained fiber had poor heat extensibility. Thus, the fibers obtained in Comparative Examples 1 to 6,
Since the heat extensibility was poor, the woven fabric composed of these fibers was inferior in soft texture.

Examples 7 to 10 and Comparative Examples 7 to 11 TiO ₂ was contained as a metal oxide in an amount of 3% by weight, the pore shape was three leaves, and the winding speed was variously changed as shown in Table 2. Using the undrawn yarn bundle obtained as described above, short fibers were produced in the same manner as in Example 2 except that the draw ratio, the draw temperature, the relaxation rate in the relaxation heat treatment, and the relaxation temperature were each changed as shown in Table 2. . In Comparative Example 7, the spinning machine stand was changed, and a spinning machine and a winding machine for high-speed spinning were used. Table 2 shows the evaluation results of the NDR of the undrawn yarn, the boiling water elongation, the dry heat elongation of the obtained short fibers, and the feeling of the woven fabric obtained from the fibers.

[0033]

[Table 2]

As is clear from Table 2, the fibers obtained in Examples 7 to 10 have excellent heat extensibility, and the woven fabric obtained from these fibers has a soft hand. there were. On the other hand, in Comparative Example 7, a fiber having excellent heat extensibility could be obtained, but the winding speed for obtaining an undrawn yarn was 2750 m / min using a spinning machine and a winder for high-speed spinning. As a result, productivity was poor. In Comparative Example 8, since the draw ratio was too high, the structure of the yarn was stabilized during drawing, and the obtained fiber was poor in heat extensibility.
In Comparative Example 9, since the stretching temperature was too low, the stretching could not be performed sufficiently, so that the yarn was frequently broken during the stretching, and the obtained fiber was inferior in quality. In Comparative Example 10, since the relaxation rate was too small, the relaxation was not sufficiently performed, and Comparative Example 11
Is not sufficiently heat-treated because the relaxation heat treatment temperature is too low, and the fibers obtained in any case are inferior in heat extensibility, and the woven fabric obtained from these fibers has a poor soft feel. there were.

[0035]

According to the present invention, by using a specific polyester low-oriented undrawn yarn, short fibers having excellent heat extensibility can be produced at low cost and with good productivity. By forming a spun yarn, knitting and weaving, and performing a finishing heat treatment or the like, it is possible to obtain a soft-textured fabric.

[Brief description of the drawings]

FIG. 1 is a partially omitted schematic process diagram showing an embodiment of the present invention.

[Explanation of symbols]

 Y Undrawn yarn bundle 1 First roller group 2 Second roller group 3 Non-contact heat treatment heater 4 Take-up roller group

Claims (1)

[Claims] 1. A method for producing a heat-extensible polyester short fiber using a polyester undrawn yarn bundle wound at a winding speed of 2500 m / min or less, comprising a metal oxide of 1% by weight or more, Unstretched yarn bundle consisting of an unstretched yarn having a cross-sectional shape of six leaves is stretched at a temperature Tg−10 to Tg + 30 ° C. at a stretch ratio of the natural stretch ratio of the unstretched yarn to the natural stretch ratio × 1.2, and continuously stretched. A thermal elongation characterized by performing a relaxation heat treatment of 5% or more at a temperature of Tg + 30 to Tg + 120 ° C., then applying a crimping and finishing oil agent to the yarn bundle, drying at a temperature of Tg or less, and cutting. Method for producing conductive polyester short fibers. However,
Tg: Glass transition temperature of undrawn yarn (℃)