JPH07173737A - Production of polyester crimped staple fiber - Google Patents

Abstract

PURPOSE:To provide a process for stabilized production of crimped polyester staple fibers showing high modulus and dimensional stability suitable for cloth spun yarns such as machine-sewing yarn or for industrial cloth such as filter cloth, particularly crimped polyester staple fibers of high modulus and low elongation which can maintain their high modulus even after heat treatment in product processing. CONSTITUTION:Polyester is melt-spun, taken up at a speed lower than 1,500m/min to form undrawn tow. The undrawn tow is drawn through a multi- stage process, for example 2 or more stages, and heat-treated at 220 to 240 deg.C under a tension or under a constant length, then forcibly cooled under the same tension as in the heat treatment down lower than the glass transition temperature and then given crimps.

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 crimped short fibers having high modulus and low shrinkage. In detail,
The present invention relates to a method for producing a high-modulus low-extension polyester crimped short fiber which exhibits high modulus and dimensional stability suitable as a spun yarn for clothing such as sewing machine threads and a short fiber for a filter, and particularly maintains a high modulus even after heat treatment during product processing. It is a thing.

[0002]

2. Description of the Related Art Polyester fiber has been widely used for industrial materials such as clothing and bedding because of its excellent properties such as heat resistance and chemical resistance. The use in the field is increasing, and further strength and dimensional stability are required. Conventionally, as a manufacturing method for obtaining a high modulus short fiber, a method in which a melt-spun undrawn tow is stretched in multiple stages at a high ratio and a heat treatment is performed at an appropriate temperature has been adopted. However, only polyester short fibers having poor dimensional stability were obtained. In order to improve the dimensional stability, a relaxation heat treatment is performed at an appropriate temperature after the tension heat treatment, or according to the description of JP-A-2-210033, the crimping temperature is set to 130 to 140 ° C. and the relaxation treatment effect is also obtained. Etc. have been adopted. However, in such a method, since the crimp is applied and the tension is relaxed when the tow temperature is equal to or higher than the glass transition temperature, the modulus is lowered and the dimensional stability is excellent, but only polyester short fibers having a low modulus are obtained.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a method for producing a polyester crimped short fiber having a high modulus and excellent dimensional stability, which can solve the above-mentioned problems of the prior art. is there.

[0004]

[Means for Solving the Problems] Means for solving the above problems, that is, the present invention, melt-spins a polyester containing ethylene terephthalate as a main constituent unit and spins at a spinning speed of 15
220 to 24 after drawing the undrawn yarn tow at multi-stages of two or more stages by taking it off at 00 m / min or less to form an undrawn yarn tow
Heat treatment at 0 ° C under tension or constant length, and
Of a polyester crimped short fiber characterized by being subjected to relaxation heat treatment at a temperature of up to 220 ° C., followed by forcibly cooling the tow kept under high temperature to a temperature below the glass transition point in a tense state, and then crimping. It is a manufacturing method.

The raw material polyester used in the present invention is
The main target is polyethylene terephthalate composed of terephthalic acid component and ethylene glycol component, but part of the terephthalic acid component may be replaced with another dicarboxylic acid component, and / or part of the ethylene glycol component may be replaced with another diol component. It may be replaced polyester. In addition, modifiers and additives may be added as necessary.

For example, the following conditions are adopted as the melt spinning conditions of the present invention. Polyester having an intrinsic viscosity of 0.55 to 0.65 is 280 to 300 ° C., preferably 285 to 29
Melt at 5 ° C. and spin. If the melting temperature is low, melt fracture and clogging of nozzle holes occur, and stable spinning cannot be performed. Further, when the melting temperature is high, thermal deterioration of the polymer proceeds, and it becomes difficult to obtain a high-strength polyester.

The spinning speed is 1500 m / min or less, preferably 1
200 m / min or less. Here, when the spinning speed exceeds 1500 m / min, the desired high modulus and low elongation properties cannot be obtained, which is not preferable.

Next, several to several tens of the undrawn yarn tows obtained as described above are bundled and sent to the drawing process.

The following conditions are adopted as the stretching conditions of the present invention. In the present invention, first, a multi-stage drawing of 2-3 stages is performed. For example, in the three-stage drawing, the first stage is in a warm bath for 2
At the third stage, drawing is performed under a high atmospheric temperature, and at the third stage, stretching is performed between heating rollers. In such a method, by gradually drawing, not only the deterioration of the drawing operability, which is a problem of the conventional method, can be improved, but also the degree of drawing of the obtained short fiber can be achieved.

The next heat treatment of the present invention is as follows. That is, heat treatment is performed at a temperature of 220 to 240 ° C. under tension or under a fixed length. The heat treatment time is required to be sufficient to increase the crystallinity of the fiber and is preferably 4.5 to
It takes 6 seconds. If the heat treatment time is lower than 220 ° C., sufficient crystallization will not be performed, and a fiber having a high modulus will not be obtained. If the heat treatment temperature is higher than 240 ° C., the fibers will melt and the operability will be significantly reduced. Further, when the heat treatment time is 4.5 seconds or less, sufficient crystallization is not performed, and a fiber having a high modulus cannot be obtained. If the heat treatment time is 6 seconds or more, the balance between spinning and drawing is lost, and the productivity is reduced. Alternatively, it is necessary to increase the number of heating rollers to be heat-treated or to increase the number of heating rollers, which requires a large amount of cost for maintenance of the equipment, which is not economical.

The relaxation heat treatment of the present invention to be performed next is as follows. That is, the heat treatment is performed in a relaxed state at a temperature of 200 to 220 ° C. This heat treatment is intended to improve dimensional stability, and the tow that has been subjected to tension or constant length heat treatment is
Relaxation heat treatment is performed at an ambient temperature of 220 ° C. for a time of 5.3 seconds or more and 7 seconds or less to remove the strain of the amorphous portion that has been subjected to the stretching and reduce the shrinkage of the fiber at a high temperature. In this case, the ambient temperature for performing the relaxation treatment is preferably lower than the tension / constant length treatment temperature. This ambient temperature is 200 ℃
If it is lower, the strain retained in the amorphous portion of the fiber cannot be sufficiently removed, and a fiber having excellent dimensional stability cannot be obtained. When the ambient temperature is higher than 220 ° C., the modulus of the crystallized portion is lowered due to the tension / constant length treatment, and the fiber has excellent dimensional stability but low modulus.

Finally, the fiber which has been subjected to the relaxation heat treatment is instantly forcibly cooled to below the glass transition point and then crimped. In the present invention, this part is the most important point. In this case, the modulus cannot be fixed sufficiently unless the temperature of the tow that has been subjected to the tension / constant length or relaxation heat treatment is lowered to the glass transition point or lower, and eventually the modulus decreases due to the tension relaxation after the crimping. To be done.

According to the present invention, melt-spun polyester undrawn yarn is subjected to multi-stage drawing, high temperature heat treatment, high temperature relaxation treatment,
By forced cooling, high-modulus low-shrinkage polyester short fibers having high orientation and excellent dimensional stability can be obtained. The polyester short fibers obtained by the method for producing such polyester short fibers have excellent physical properties such as high strength and low elongation, and retain excellent dimensional stability. It is extremely suitable as a short fiber for filters, and the drawing operability is remarkably improved by such a production method.

[0014]

The present invention will be described in detail with reference to the following examples. The methods for measuring physical properties used in the evaluation of the present invention are as follows. Breaking strength, breaking elongation: Thread length of 50 according to Tensilon
mm and a pulling speed of 20 cm / min. Strength after 10% elongation after boiling water treatment: Wrap the sample in a cloth, soak it in hot water at 130 ° C for 30 minutes, take it out, and lightly drain the water with absorbent paper. After air-drying, the strength at 10% elongation is measured by the above tensile tester. Dry heat shrinkage ratio: After measuring the length L0 under the initial load of 1/15 g / d, dry heat treatment was carried out at 160 ° C. for 30 minutes, and the length L1 was measured under the same load and calculated from the following formula. . Dry heat shrinkage (%) = L0-L1 / L0 × 100 Intrinsic viscosity (IV): Measured using an Ostwald viscometer as an orthochlorophenol solution.

Example 1 Two polyethylene terephthalates having an intrinsic viscosity of 0.63 were used.
Melts at 90 ° C, discharges from the spinneret from a gear pump,
An undrawn yarn having a thickness of 4.2 denier was prepared by receiving the tow can at a spinning speed of 1100 m / min. Next, this unstretched yarn is heated to 70 ° C.
In the warm bath of 1st step, 2nd step in 170 ° C atmosphere, 3rd step between 220 ° C heating rollers and 6 seconds heat treatment, 4 seconds x 7 seconds relaxation in 200 ° C atmosphere After heat treatment and forced cooling to 30 ° C. with a cooling roller, the drawn yarn was heated again to 95 ° C., crimped by a crimper, and cut to obtain polyester short fibers. Table 1 shows the drawing conditions, the heat treatment conditions, the cooling conditions, the physical properties of the obtained fibers, and the drawing operation conditions used in this example.

Example 2 The same undrawn yarn as in Example 1 was drawn in the same manner as in Example 1 in the first and second stages, and then drawn in a third stage between heating rollers at 220 ° C. and heat-treated for 4.5 seconds. 4% x at 180 ℃
Relaxation heat treatment for 5.3 seconds, and polyester short fibers were obtained in the same manner as in Example 1. Table 1 shows the drawing conditions, the heat treatment conditions, the cooling conditions, the physical properties of the obtained fibers, and the drawing operation conditions used in this example.

Comparative Example 1 The same undrawn yarn as in Example 1 was drawn in a hot bath at 70 ° C. for the first stage, second stage in an atmosphere of 170 ° C., heat treated for 6 seconds with a heating roller at 220 ° C., and 200 ° C. 4% under the atmosphere of
A relaxation heat treatment was performed for 7 seconds, followed by crimping with a crimper while keeping the temperature of the tow at the glass transition point or higher with a heating roller, and cutting the polyester to obtain polyester short fibers. Table 1 shows the drawing conditions, the heat treatment conditions, the cooling conditions, the physical properties of the obtained fibers, and the drawing operation conditions used in this example.

Comparative Example 2 The same undrawn yarn as in Example 1 was drawn in a 70 ° C. hot bath in the first stage, drawn in a 170 ° C. atmosphere in the second stage, and heat-treated with a heating roller at 220 ° C. for 4.5 seconds. 4 at 200 ℃
% × 5.3 seconds, followed by crimping with a crimper while keeping the temperature of the tow above the glass transition point with a heating roller, and then cutting the polyester to obtain polyester short fibers. Table 1 shows the drawing conditions, the heat treatment conditions, the cooling conditions, the physical properties of the obtained fibers, and the drawing operation conditions used in this example.

[0019]

[Table 1]

[0020]

As described above, the polyester short fibers produced by the production method of the present invention have high modulus and low shrinkage, and are expected to have high-speed sewing resistance and dimensional stability, and for spun yarns such as sewing yarns, or It is extremely useful for producing raw cotton for filters.

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Claims (1)

[Claims] 1. A polyester containing ethylene terephthalate as a main constituent unit is melt-spun and the spinning speed is 1500 m /
The unstretched yarn tow is taken up in less than a minute to form an unstretched yarn tow, and the unstretched yarn tow is stretched in two or more stages, and then heat-treated at a temperature of 220 to 240 ° C. under tension or a fixed length, and further 200 to 220.
A method for producing a polyester crimped short fiber, which is characterized by performing relaxation heat treatment at a temperature of ℃, and subsequently forcibly cooling the tow kept at a high temperature to a temperature below the glass transition point in a tension state, and then crimping. .