JPH07305225A - Highly shrinkable polyester staple fiber and method for producing the same - Google Patents

Abstract

PURPOSE:To obtain highly shrinkable polyester staple fibers having a high thermal shrinkage constant, little in the changes of the quality with time, excellent in stability, and suitable for base fabrics used for artificial leathers, etc., by subjecting a polyethylene terephthalate to spinning, drawing and post-treating processes under specific conditions. CONSTITUTION:The highly shrinkable polyester staple fibers are obtained by melt-spinning a polymer substantially comprising a polyethylene terephthalate, blowing <=40 deg.C cold air on the side surface of the spun fiber bundle at a position lower by 10-100mm than the surface of a nozzle at a wind speed of 0.5-2.00m/sec, drawing the quenched undrawn fibers to a length of 2.5-3.0 times in <70 deg.C water, and subsequently subjecting the drawn fibers to post-treatments including a staple fiber-forming process in an atmosphere not exceeding 70 deg.C. The obtained objective highly shrinkable polyester staple fibers have a shrinkage constant of >=20%, in boiling water, a crystal orientation degree of 77-82%, an amorphous part orientation degree of 54-64%, and a crystallinity of 15-22%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel polyester fiber and a method for producing the same. More specifically, the present invention relates to a highly shrinkable polyester fiber which is excellent in stability over time and is useful as a non-woven cloth or spun yarn, and a method for producing the same.

[0002]

2. Description of the Related Art Polyester fiber is spun at a high speed or stretched in warm water at a low ratio to destabilize the structure to produce a fiber having a high heat shrinkage ratio, and shrink it in the subsequent step. The method of densifying or imparting swelling or core / sheath structure to the spun yarn is conventionally known.
For example, in Japanese Patent Laid-Open No. 55-112356, an undrawn polyester yarn is used in a warm water bath at 55-60 ° C. for 2.4-
It is described that it is stretched 2.8 times and then crimped to form a staple without being exposed to a temperature of 60 ° C. or higher.

In Japanese Patent Publication No. 62-46662, a polyester is melt-spun, then drawn in warm water of 60 to 65 ° C. by a factor of 2.4 to 2.7 and dried at 65 ° C. or less. It is described that a latent highly shrinkable polyester fiber that shrinks 45% or more in an atmosphere of 180 ° C. is obtained.

[0004]

However, the structure of the highly shrinkable polyester fibers according to the prior art is likely to change, and the physical properties and quality of the highly shrinkable polyester fibers are sensitively reflected by the fluctuation of the conditions during storage and transportation. Therefore, the deterioration of quality cannot be avoided. The present invention has been made in view of such circumstances, and the purpose thereof is to:
Even under environmental conditions such as long-term storage and long-distance transportation in ordinary packaging, the structural change is extremely small,
It is an object of the present invention to provide a highly shrinkable polyester fiber having practically the same stability as product resistance as general polyester fibers and a method for producing the same.

[0005]

The present invention has a crystal orientation of 77 to 82%, an amorphous orientation of 54 to 64%, a crystallinity of 15 to 22%, and shrinkage in boiling water. % Of at least 20% is a highly shrinkable polyester staple fiber consisting essentially of polyethylene terephthalate, wherein such polyester staple fiber comprises a polymer consisting essentially of polyethylene terephthalate. In melt spinning, cold air at 40 ° C. or less is blown onto the side surface of the fiber bundle from a position 10 to 100 mm lower than the nozzle surface at a wind speed of 0.5 to 2.0 m / sec to rapidly cool the undrawn yarn. After being spun, and then drawn 2.5 to 3.0 times in water below 70 ° C., and subjected to post-treatment including stapling in an atmosphere not exceeding 70 ° C., the shrinkage ratio in boiling water is at least 20.
% Polyester fiber.

The polyester used in the present invention consists essentially of polyethylene terephthalate, that is, it contains 80 mol% or more of ethylene terephthalate units and may contain additives such as titanium oxide. The polyester fiber of the present invention has a boiling water shrinkage of 20% or more, but has high stability at room temperature, and in order to have such properties,
It is necessary that the polyester fiber satisfy all the requirements of the crystal orientation degree, the amorphous orientation degree, and the crystallinity degree specified in the present invention.

That is, when the crystal orientation degree exceeds 82% or the amorphous orientation degree exceeds 64%, the dimensional stability in the low temperature region is improved, but in the higher temperature region, the shrinkage is repeated again, and thus the dimensional stability is increased. Lack of stability in the area. On the other hand, when the crystal orientation degree is 77% or the amorphous orientation degree is less than 54%, the desired high shrinkability cannot be exhibited even by heating. Further, if the crystallinity exceeds 22%, it is preferable for stabilizing the structure over time, but the heat shrinkage force is not sufficient. On the other hand, if the crystallinity is less than 15%, the fixing points in the fiber are insufficient, so that the structural stabilization during storage and transportation, which is the object of the present invention, cannot be achieved.

The above-mentioned crystal orientation degree, amorphous orientation degree and crystallinity degree are subtly changed depending on the draw ratio and the heat history during spin-drawing. Therefore, appropriate conditions for producing the polyester fiber of the present invention are set. It will be necessary to choose. Hereinafter, the method of the present invention will be described, but the outline of the characteristic part of the method of the present invention is to carry out three processes of quenching spinning, wet drawing, and low temperature heat treatment in order, and in particular, a specific amorphous orientation structure by the quenching spinning method It is important to spin polyester fibers with That is, by blowing cold air directly below the spinning nozzle, the molecules of the polyester fiber in the molten state are frozen, and the structure is fixed while maintaining the amorphous orientation.
By subsequently subjecting it to a stretching step, the above-mentioned degree of amorphous orientation can be obtained.

Details of the quench spinning method are as follows. In the case of ordinary melt spinning of polyethylene terephthalate, the spinning speed is 500 to 2000 m / min, and the melt spinning temperature is 30.
The temperature is around 0 ° C, and the cold air blowing position to cool it is
It is desirable that the point immediately below the base and as close to the nozzle surface as possible be desirable. However, if it is too close to the nozzle surface, the operability will be significantly reduced. Therefore, in order to maintain production efficiency, a blowing position is provided at a point 10 to 100 mm, preferably 30 to 60 mm away from the nozzle surface, and cooling air is blown to the side surface of the spun fiber bundle. Regarding the blowing method of cooling air, various proposals have hitherto been made, and in addition to the method of directly blowing, the method of producing an annular airflow or the method of blowing the spun fiber bundle at an angle However, there is no particular limitation as long as the cooling effect is not significantly impaired.

Next, the volume, speed and temperature of the cold air are also important. Especially, the temperature has a great influence on the fiber structure and physical properties, and a temperature lower than 40 ° C. is necessary. If the temperature exceeds 40 ° C., the effect of quenching is small, so it is necessary to increase both the air volume and the air speed to obtain the desired structure, which makes stable operation difficult. The wind speed of cold air is above the blowing position and temperature,
Of course, it changes depending on the fineness of the fiber to be spun and the discharge amount,
When spinning a tow having an ordinary total fineness of about 2000 to 10000 denier, it is suitable to set it to 0.5 to 2.0 m / sec from the balance of operability and polyester fiber structure formation.

When the undrawn yarn is obtained by the melt spinning and the rapid cooling as described above, the drawing is continued, and this may be continuously carried out without winding or may be carried out once. . However, the stretching needs to be performed by a wet stretching method. That is, crystallization is properly suppressed, and
This is because wet stretching in warm water at a low temperature is more effective than dry heat stretching to increase the amorphous orientation.

Naturally, the temperature of the hot water must be raised to around the glass transition temperature of the polyester fiber, but it must be 70 ° C. or lower. Because, when stretched in warm water, water molecules act inside the fiber to increase the mobility of the polyester molecular chains in the amorphous region, so that the above-mentioned amorphous orientation can be achieved when the temperature exceeds 70 ° C. Because there is no. The draw ratio must be 2.5 to 3.0 times that of ordinary undrawn yarn, and it is preferable to draw uniformly at a constant draw ratio in order to obtain highly stable fibers.

The stretched fibers are crimped by a mechanical crimping method or the like and then subjected to post-treatments such as drying and stapling in an atmosphere not exceeding 70 ° C. The polyester short fibers obtained as described above can be made into a non-woven fabric by the nidle punch method or the like, and can be made into a mixed yarn with various fibers, and these non-woven fabrics and mixed yarns are heated in boiling water or hot air. When it goes through, the polyester fiber is 20
In the case of a non-woven fabric that shrinks by more than%, a homogeneous and high-density product can be obtained. When the blended yarn is exposed to a high temperature atmosphere as described above, the polyester fiber of the present invention shrinks and converges on the core of the yarn, and a bulky core-sheath structure yarn in which other fibers are distributed in the outer layer. Become.

[0014]

EXAMPLES Next, the present invention will be explained with reference to examples, but the present invention is not limited to the examples. The method of measuring the physical properties referred to in the present invention is as follows. Crystallinity: The crystallinity is calculated by the following formula from the measured fiber density using a density gradient tube made of carbon tetrachloride / n-heptane.

[0015]

## EQU1 ## Crystallinity (%) = (dob-da) / (dc-
da) × 100 where dob: measured density g / cm ³ dc: crystal density 1.455 g / cm ³ da: amorphous density 1.335 g / cm ³ degree of crystal orientation: half value of orientation distribution function of (100) plane The degree of crystal orientation was calculated from the width by the following formula.

[0016]

## EQU00002 ## Crystal orientation degree (%) = half width of (100) plane /
180 × 100 Amorphous orientation degree: Using the birefringence measured by a polarizing microscope equipped with a Berek type compensator and the crystallinity degree and the crystal orientation degree, the amorphous orientation degree was calculated by the following formula. Here, the intrinsic birefringence of the crystal part is 0.22
On the other hand, the intrinsic birefringence of the amorphous part was 0.276.

[0017]

## EQU00003 ## Amorphous orientation degree (%) = (nob-X / 100.fc / 10
0 · nco) / ((1-X / 100) · nao) × 10
0 where nob: measured birefringence, nco: intrinsic birefringence of crystal part, nao: intrinsic birefringence of amorphous part, X: crystallinity (%) fc: crystal orientation (%)

Heat shrinkage ratio: Each short fiber was fixed to the sample table with slack, and treated in a hot air dryer for 170 × 15 minutes, and then measured according to JIS L-1015. Shrinkage rate of boiling water: Polyester fiber was dipped in boiling water in a tension-free state for 15 minutes, heat treated, taken out, air-dried, and measured according to JIS L-1015.

Example 1 A polyethylene terephthalate having an intrinsic viscosity of 0.64 (measured in a mixed solvent of phenol / tetrachloroethane = 6/4 at 20 ° C.) prepared by a conventional method was used at a spinning temperature of 290.
The spinneret with 4500 spinning holes at ℃ spun at a discharge rate of 2000 g / min and a spinning speed of 950 m / min, and the spun yarn was spun from the position about 60 mm below the spinneret to 26 ° C.
It was rapidly cooled by applying cooling air having a wind speed of 1.3 m / sec.

The undrawn yarn thus obtained was aligned in a tow shape of 1 million denier, drawn in water at 65 ° C. to about 2.7 times, mechanically crimped, and then dried at 60 ° C. It was cut into 51 mm to obtain a polyester staple. Table 1 shows the yarn quality and structure / physical property values of the staple, and the physical property values measured after standing at room temperature for 100 days.

Comparative Example 1 The undrawn yarn obtained in Example 1 was treated with 1 million denier.
The polyester staples were obtained by aligning them in a tow-like shape, stretching them to about 2.7 times with a roller heated to 75 ° C., applying mechanical crimping, and then cutting them into 51 mm. Table 1 shows the yarn quality and structure / physical property values of the staple, and the physical property values measured after standing at room temperature for 100 days.

Comparative Example 2 A polyethylene terephthalate having an intrinsic viscosity of 0.64 (measured in a mixed solvent of phenol / tetrachloroethane = 6/4 at 20 ° C.) prepared by a conventional method was used at a spinning temperature of 290.
Spinning at a spinneret having 2300 spinning holes at 2 ° C at a discharge rate of 2300 g / min and a spinning speed of 900 m / min, the spun yarn is spun at a temperature of about 60 mm below the spinneret at 28 ° C.
It was rapidly cooled by applying cooling air having a wind speed of 0.8 m / sec.

The undrawn yarn thus obtained was aligned in a tow shape of 1 million denier, drawn about 4.2 times with a roller heated to 80 ° C., mechanically crimped, and then cut into 51 mm. A polyester staple was obtained. Table 1 shows the yarn quality and structure / physical property values of the staple, and the physical property values measured after standing at room temperature for 100 days.

[0024]

[Table 1]

Examples 2 to 3 and Comparative Examples 3 to 7 The undrawn yarn tow of Example 1 was stretched, mechanical crimps were applied by variously changing the post-process conditions, and then dried under the same conditions as in Example 1. It was cut to obtain a polyester staple. Table 2 collectively shows these yarn qualities, structure / physical property values, and physical property values measured after standing at room temperature for 100 days, together with manufacturing conditions.

[0026]

[Table 2]

Example 4 A mixed yarn obtained by mixing 1: 1 of polyester staple and cotton yarn obtained in Example 1 was used as a weft yarn, and a mixed yarn of Comparative Example 1 was obtained by mixing 1: 1 of polyester staple and cotton yarn. A plain woven fabric was woven into warp yarns. The plain woven fabric was scoured and bleached, put on a steam setter, fed in the warp direction by 0 to 5% and contracted in the weft direction by 10 to 20% to obtain a final product.
The obtained plain woven fabric was rich in weft tension, and had a soft and dry-touch texture. When the cross section of the weft of the woven fabric was observed with an electron microscope, polyester staples were converged on the yarn center layer, and cotton yarn was distributed in the outer layer portion at a ratio of 50% or more.

[0028]

EFFECTS OF THE INVENTION The polyester short fiber of the present invention has a high heat shrinkage ratio, is excellent in stability during storage and transportation, and has little quality fluctuation with time. In particular, it is a base fabric for artificial leather. When used as, a soft and natural leather-like texture is obtained. Further, according to the method of the present invention, the polyester short fibers can be stably and easily produced, and its usefulness is clear.

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Claims (2)

[Claims] 1. A crystal orientation degree of 77 to 82%, an amorphous orientation degree of 54 to 64%, a crystallinity degree of 15 to 22%, and a shrinkage ratio in boiling water of at least 20%. A highly shrinkable polyester staple fiber consisting essentially of polyethylene terephthalate. 2. When melt-spinning a polymer consisting essentially of polyethylene terephthalate, 1 from the nozzle surface
From a position lowered by 0 to 100 mm, cold air of 40 ° C. or less is blown onto the side surface of the fiber bundle at a wind speed of 0.5 to 2.0 m / sec to rapidly cool the undrawn yarn, and then to a temperature of less than 70 ° C. A polyester fiber having a shrinkage ratio of at least 20% in boiling water is obtained by performing post-treatment including stretching in an atmosphere that does not exceed 70 ° C. by stretching 2.5 to 3.0 times in water. A method for producing a high-shrinkage polyester staple fiber, which is characterized.