JPH04361610A - Production of polyester fiber - Google Patents

Abstract

PURPOSE:To produce the subject fiber having excellent strength, elongation, heat resistance, etc., by melt-spinning a specific polyethylene terephthalate, cooling the spun fiber, allowing the fiber to run in a heated zone, drawing, thermally treating and subsequently taking the treated fiber on a roll. CONSTITUTION:Polyethylene terephthalate copolymerized with a >=8C aliphatic dicarboxylic acid in an amount of 2-20mol.% based on all carboxylic acids is melt-spun through a spinneret and at once cooled with cold air to a temperature below the glass transition temperature of the copolymer. The fiber is introduced into a heating zone to again heat the fiber to a temperature between the glass transition temperature and the melting point of the copolymer, drawn, treated with heat and subsequently taken on a roll at a taking rate of >=6200m/min to provide the objective fiber.

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 polyester fibers, and more particularly to a method for producing polyester fibers having excellent physical properties using an ultrahigh-speed spinning method.

0002

BACKGROUND OF THE INVENTION Polyester fibers, particularly polyethylene terephthalate fibers, have excellent heat resistance, chemical resistance and mechanical properties, and are therefore widely used in clothing and industrial applications. Ordinary polyester fibers for clothing with a single filament denier of about 2 to 3 deniers are produced by extruding molten polyester into fibers from a spinneret.
It is manufactured through two steps: spinning and stretching, which involve winding at a take-up speed of m/min, then stretching and heat setting.

[0003] In recent years, a high-speed spinning method has been developed with the aim of improving productivity by increasing the take-up speed to 4000 m/min or more, thereby making it possible to obtain fibers that fully satisfy practical properties without going through a drawing process. It has been put into practical use. This high-speed spinning method includes two methods: (1) an ultra-high-speed spinning method in which the yarn melt-spun from a spinneret is taken directly at a speed of 5,000 m/min or more without being reheated; (2) a method in which the yarn is melt-spun from a spinneret and taken directly at a speed of 5,000 m/min or more; A hot tube draw-spinning method in which the fibers are drawn and heat-treated while being reheated and taken off at a speed of 4000 m/min or more;
There is a direct spinning/drawing method in which the material is stretched between a take-up roll and taken off at a speed of 3000 m/min or more. These high-speed spinning methods are expected to reduce costs, such as simplifying equipment, saving space, saving energy, and reducing the number of required personnel, by eliminating the need for the conventional drawing process, and also significantly increasing the take-up speed. Therefore, a significant improvement in productivity is expected.

[0004] Among these methods, compared to the ultra-high-speed spinning method, the hot tube draw-spinning method does not cause a sudden change in the yarn speed just below the spinneret, and therefore has fewer yarn breakages. There are advantages such as the ability to obtain fibers having almost the same physical properties as the drawn yarn that has undergone the process. Furthermore, compared to the direct spinning/drawing method, there are advantages such as the ability to reduce the number of rolls and no need to use heating rolls, which allows production at low cost. Thus, the hot tube draw-spinning method can be said to be an excellent spinning method among high-speed spinning methods. However, when the take-up speed is increased in order to further improve productivity, in the hot tube draw-spinning method, necking deformation peculiar to high-speed spinning occurs above the heating zone, and the yarn speed at the entrance of the heating zone suddenly decreases. It was clear that the price would be higher. As a result, thread breakage occurs frequently and the spinning performance is significantly reduced, and productivity is not improved but rather reduced. When the yarn speed at the entrance of the heating zone exceeds 4500 m/min, oriented crystallization progresses during the cooling process, the amorphous part relaxes and the crystal size increases, and the cooling rate of the yarn is high, so the yarn There is a temperature difference between the surface layer and the inside of the fiber, and the fiber structure changes between the surface layer and the inside, and the physical properties of the fiber change to be similar to those of fibers obtained by ultra-high speed spinning. For this reason, the advantage of production using the hot tube draw-spinning method, which provides physical properties equivalent to those of conventional drawn yarns, is almost completely eliminated. For this reason, it has been difficult to spin fibers using the hot tube draw-spinning method at a speed exceeding the current take-up speed, which has become one of the technical barriers.

[0005] Using this hot tube draw-spinning method,
There are several examples of increasing the take-up speed to 6000 m/min or higher. Japanese Patent Publication No. 51-147613
The patent publication divides the yarn to separate the accompanying air current, and furthermore, by keeping the drawing ratio low and increasing the heating zone entrance speed, the tension of the yarn entering the heating zone is increased to prevent yarn shaking and disturbances in the yarn path. I tried to suppress it as much as possible. Therefore, in the publication, in the case of a take-up speed of 6000 m/min, the heating zone inlet speed is set to 4500 m/min or more, that is, approximately 4600 m/min.
/min to 5,700m/min. When ordinary homopolyethylene terephthalate (homo-PET) is applied to this process, the heating zone entrance velocity is normally at this level, and at this speed necking occurs essentially before the hot tube entrance. As mentioned above, it is thought that the physical properties of the fibers have changed to those of the fibers obtained by ultra-high speed spinning. For this reason, not only are physical properties similar to those of conventional drawn yarns not obtained, but there is a risk that yarn breakage will occur frequently and that the yarn-spinning properties will deteriorate. As mentioned above, these behaviors are essential problems of homo-PET, and are difficult to overcome by changing the spinning conditions.

In addition, Japanese Patent Publication No. 58-3049 discloses that by providing a heating zone with a high temperature higher than the melting point of the polymer immediately below the spinneret and controlling the cooling and reheating temperature of the yarn, it is possible to draw the yarn at a speed of 6000 m/min or more. is proposed. However, since this method requires two heating zones with different temperatures, it requires two heating devices, making the device large-scale and complicated. In addition, repair work for the cap to remove dirt generated on the cap surface and maintenance management become complicated. Furthermore, since the atmosphere directly under the nozzle is quite high temperature, decomposition products from the discharged polymer will sublimate rapidly, resulting in dirt on the nozzle surface and reduced uniformity in the longitudinal direction of the yarn and between single yarns. It is thought that this will lead to In addition, in this method, the reheating process is performed after the filament is focused.
Heat tends to be applied unevenly between single yarns, and heat treatment spots may occur. In this way, up until now, speeding up the hot tube draw-spinning method has only been investigated by changing the spinning method, and there have been no attempts to speed up the hot tube draw-spinning method by actively changing the components of the spun yarn. The improvement effect was not sufficient.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing polyester fibers that can be drawn at a higher speed than conventional methods using the hot tube draw-spinning method described above, and that have excellent properties comparable to conventional drawn yarns. be. Another object of the present invention is to provide a method for producing polyester fibers that has stable yarn quality without breakage even when taken at a higher take-up speed than conventional methods, has high productivity, and has excellent spinning properties. be.

[0008]

[Means for Solving the Problems] The object of the present invention is to melt-spun polyethylene terephthalate, which is a copolymerized aliphatic dicarboxylic acid having 8 or more carbon atoms from 2 to 20 mol% based on the total dicarboxylic acids, from a spinneret, and After once cooling down to below the transition temperature, the yarn is run through a heating zone, and the yarn is reheated to a temperature above the glass transition temperature and below the melting point for drawing heat treatment, and a first take-up roll with a take-off speed of 6200 m/min or more. This can be achieved by a method for producing polyester fiber, which is characterized in that it is drawn off at

The present invention will be explained in detail below. The greatest feature of the present invention is that by using a specific copolymerized polyester as a polyester raw material in hot tube draw spinning, yarns with excellent physical properties and homogeneity can be produced at high speeds without compromising spinnability. This is the first time that this has been achieved. This is because in the hot tube draw-spinning method, when the speed of homo-PET is increased, necking deformation occurs at the entrance side of the hot tube as described above, and the yarn speed reaches a high speed of 4,500 m/min or more. However, when the polyester of the present invention is used, the molecular chain is changed by the copolymerized dicarboxylic acid component. This is because, even if the take-up speed is increased, the yarn speed at the hot tube entrance can be kept at about the conventional speed. This has made it possible to obtain yarn with strength, elongation, and birefringence values comparable to those of conventional drawn yarn even at higher speeds.

The main dicarboxylic acid component constituting the polyester of the present invention is a terephthalic acid component, and 2 to 20 mol % of the total dicarboxylic acid component is an aliphatic dicarboxylic acid having 8 or more carbon atoms. The polyester used in the present invention has the above-mentioned terephthalic acid component and aliphatic dicarboxylic acid component having 8 or more carbon atoms as essential dicarboxylic acid components, but other dicarboxylic acid components may be used within the scope of the purpose of the present invention. May be used together. However, it is desirable that aromatic dicarboxylic acids and the like are not included since they may impede the object of the present invention. The main diol component constituting the polyester of the present invention is ethylene glycol, but other components such as 1,4-butanediol, 1,6-hexanediol, polyethylene glycol, polytetramethylene glycol, 1,4- A diol component such as cyclohexanedimethanol may be used in combination without departing from the purpose of the present invention.

The aliphatic dicarboxylic acid component having 8 or more carbon atoms in the present invention is an aliphatic dicarboxylic acid having 8 or more carbon atoms between its two carboxyl groups, including the carbon atoms constituting the carboxyl group. It is a component and may be linear or branched. Specific examples include suberic acid (carbon number = 8), azelaic acid (carbon number = 9), sebacic acid (carbon number = 10), dodecanedioic acid (carbon number = 12), brassylic acid (carbon number = 13), Eicosandioic acid (number of carbons =
20), aliphatic dicarboxylic acid components such as dimer acid (carbon number = 36, etc.). It is preferable to use an aliphatic dicarboxylic acid component having 8 to 36 carbon atoms because when subjected to high-speed spinning, fibers with better mechanical properties such as strength, elongation, and Young's modulus can be obtained. From the viewpoint of the mechanical properties of the obtained fiber, it is more preferable to use an aliphatic dicarboxylic acid component having 8 to 22 carbon atoms.
It is even more preferable that the copolymerization component is an aliphatic dicarboxylic acid having 8 to 12 carbon atoms. The above aliphatic dicarboxylic acid components may be used in combination. In addition, in the present invention, the amount of the aliphatic dicarboxylic acid component described above is 2 to 20% of the total dicarboxylic acid component constituting the polyester.
The content is preferably 20 mol%, and 6 to 13 mol% from the viewpoint of cost and improvement effect on the mechanical properties of the resulting fibers. If it is less than 2 mol%, little improvement effect on the mechanical properties of the obtained fibers will be obtained, and if it is less than 20 mol%
If it exceeds this amount, even if the copolymerization is performed, the mechanical properties of the resulting fibers will not improve, and the heat resistance will be low, resulting in problems in spinning properties. The polyester of the present invention also contains various additives, such as matting agents, flame retardants, antioxidants,
An ultraviolet absorber, an infrared absorber, a crystal nucleating agent, a fluorescent brightener, etc. may be copolymerized or mixed as necessary.

The copolyester of the present invention can be specifically produced by the following method. That is, esterification reaction between terephthalic acid and ethylene glycol, transesterification reaction between dimethyl terephthalate and ethylene glycol,
Alternatively, bis(2-hydroxyethyl terephthalate) and/or its low polymer is synthesized by an addition reaction between terephthalic acid and ethylene oxide, and then this is polycondensed under heating and reduced pressure until a predetermined degree of polymerization is reached. In the normal production process of polyethylene terephthalate, for example, at any stage before the completion of the polycondensation reaction, an aliphatic dicarboxylic acid component having 8 or more carbon atoms is added to a dicarboxylic acid or a lower alkyl dicarboxylic acid. It can be produced as an ester by adding it to the above reaction system and copolymerizing it. At this time, the aliphatic dicarboxylic acid component having 8 or more carbon atoms, which is a copolymerization component, may be added in powder form, or after being dispersed, dissolved, or heat-treated in a suitable solvent such as ethylene glycol.

The polyester thus obtained is melt-spun. First, the polyester melted and discharged from the spinneret is once cooled to below the glass transition temperature by cooling air. Cooling is performed until the temperature at which the polyester yarn solidifies, that is, below the glass transition temperature, so that the subsequent drawing heat treatment can be performed stably. The distance from the mouthpiece to the heating zone inlet should be between 0.5 and 100% to provide sufficient cooling under the mouthpiece, workability, and sufficient tension created by air resistance forces.
4.0 m is preferable, and 1.0 to 3.0 m is more preferable.

[0014] The once cooled yarn is introduced into a heating zone, reheated, and subjected to drawing heat treatment. In order to allow the yarn to stretch freely in the heating zone, it is preferable that the yarn is not brought into contact with anything other than the yarn path regulating section at the entrance or exit. Preferably, the heating cylinder is one that is heated from the surroundings, one that is filled with heated dry hot air, saturated steam or heated steam, or a combination of these. In the heating zone, necessary and sufficient tension and temperature are required for the passing yarn to be subjected to drawing heat treatment.

[0015] The heating temperature is preferably a temperature at which the fiber maintains its practical strength and does not cause processing unevenness in the yarn, and is difficult to limit due to the relationship with the stretching ratio of the yarn, but it is necessary for stretching to occur. The temperature of the heating zone needs to be 50 to 80°C or higher. Further, for more sufficient heat treatment, a temperature of 105°C or higher, preferably 110°C or higher is required. At this time,
Even if stretching occurs, if sufficient heat treatment does not occur, the boiling water shrinkage rate will exceed 30%, resulting in poor dimensional stability. The upper limit temperature of the heating zone is determined by the melting point, because if the heating temperature is close to the melting point of the yarn, the uniformity between the single yarns in the longitudinal direction of the fiber may decrease and it may not be possible to obtain a homogeneous yarn. Below, the temperature is preferably 250°C or less, and from the viewpoint of energy cost, 200°C or less is preferable.

[0016] Stretching heat treatment is occurring when the peak temperature of heat shrinkage stress is 105°C or higher, preferably 110°C.
This can be confirmed by the fact that the thermal shrinkage stress is 0.3 g/d or more. Stretch heat treatment refers to stretching and subsequent heat treatment. For stretching to occur, sufficient tension necessary for stretching must be applied to the yarn;
It is also necessary that sufficient heat be supplied from the heating zone. The tension here is (actual tension of the multifilament at the entrance of the heating zone) ÷ (denier of the winding yarn), and it is calculated by taking into account the single yarn denier of the winding yarn, the take-up speed, the distance from the nozzle to the heating zone, etc. The tension required for stretching is usually 0.3 g/d or more, although it varies depending on the material. If it is less than 0.3 g/d, stretching will be insufficient and mechanical properties will deteriorate. The length of the heating zone is preferably 0.5 to 3.0 m from the viewpoint of stable stretching heat treatment and energy cost.
．． 0 to 2.0 m is more preferable.

[0017] The take-off speed is determined in consideration of the mechanical properties of the fibers obtained, yarn breakage, productivity improvement, etc. In the copolymerized polyester of the present invention, if the drawing speed is low, the drawing will be insufficient and the birefringence index will be less than 0.13, making it impossible to obtain a fiber that satisfies practical properties. There is. With the polyester of the present invention, at the above-mentioned take-off speed, a yarn with physical properties equivalent to those of the drawn yarn obtained by the conventional method can be obtained, and it is possible to improve the productivity of polyester fibers. Taking into consideration the mechanical properties of the resulting fibers, the disadvantages of deterioration in spinning properties due to yarn breakage due to increased speed, and the advantages of improved productivity, the take-up speed is 9000 m.
/min or less is preferable.

The reason why the physical properties of the fiber obtained by the method of the present invention are excellent even when a high-speed spinning method in the above-mentioned take-up speed range is adopted is that the fiber has a high content of methylene groups having 8 or more carbon atoms. Because a relatively large amount of group dicarboxylic acid components are copolymerized, the concentration of aromatic rings contained per unit volume of polyester is lower than that of ordinary polyester, and the flexibility of the molecular chain is increased. Since the interaction between the two is small, there are few restraining points during stretching, and the restraining force is weak, oriented crystallization is difficult to occur even when subjected to high-speed spinning, and the stretching ratio can be set high, so even at higher speeds than before, it is comparable to conventional drawn yarn. It is believed that fibers with excellent physical properties can be obtained.

[0019]

[Example] Each characteristic value in the example was determined according to the following method. (A) Fiber strength and elongation It was determined from the load-elongation curve using a Tensilon tensile tester manufactured by Toyo Baldwin. (B) Using a birefringence interference microscope (manufactured by Carl Zeiss), the refractive index in the direction parallel (nh) and perpendicular (np) to the fiber axis was determined from the light passing through the diameter of the fiber, and the birefringence Δn = nh
- np. (C) Silk-spinning property Evaluation was based on the number of thread breakages when spinning 1000 kg of thread. ◎: When the number of thread breakages is 0 to 1 times ○: When the number of thread breakages is 1 to 2 times △: When the number of thread breaks is 3 to 5 times ×: When the number of thread breaks is 6 or more times Example 1, Comparative Example 1 Using 75 parts by weight of ethylene glycol, 150 parts by weight of terephthalic acid, and 20 parts by weight of sebacic acid (10 mol % based on the total dicarboxylic acid) as copolymerization components, a low polymer obtained by a normal esterification reaction was added to prevent coloration. A polycondensation reaction was carried out by adding 0.03 parts by weight of an 85% aqueous solution of orthophosphoric acid as an agent, 0.06 parts by weight of antimony trioxide as a polycondensation catalyst, and 0.06 parts by weight of cobalt acetate tetrahydrate as a toning agent. A copolymerized polyester was obtained. This polymer was melted at 290° C. and discharged from a nozzle with 24 holes. Cooling air at 25°C at 25m/min is applied to the yarn discharged from the nozzle.
After applying the yarn over a length of 2.0 m and once cooling it to room temperature, a wire with a length of 2.0 m and an inner diameter of 20
The yarn was introduced into a heating cylinder of mmφ. At this time, the temperature of the inner wall of the heating cylinder was set at 200°C. 50 threads were taken
Polyester fibers were obtained by changing the discharge amount and take-up speed so that the filament thickness was denier/24.

In addition, a non-copolymerized homopolyester fiber was prepared from 75 parts by weight of ethylene glycol and 166 parts by weight of terephthalic acid in exactly the same manner as above.

Table 1 shows the birefringence index (Δn
) values, strength, elongation, Young's modulus, hot tube entrance yarn speed, and spinnability.

[0022]

[Table 1]

As is clear from Table 1, in Comparative Example 1, in which no copolymer component was added, Δn was much less than 0.13 at a take-up speed of 5500 m/min or more, and the strength and elongation were comparable to that of conventional drawn yarn. On the other hand, the high-speed spun fiber obtained in Example 1, which is the copolymerized polyester of the present invention, has Δn ≧0.13 even at a take-up speed of 6200 m/min or more. It shows practically sufficient fiber physical properties in terms of strength and elongation, and has good spinning properties.

Examples 2 and 3 Comparative Examples 2 and 3 75 parts by weight of ethylene glycol, 150 parts by weight of terephthalic acid, and aliphatic dicarboxylic acids (10 mol % based on the total dicarboxylic acids) or isophthalic acids shown in Tables 2 and 3. A low polymer obtained by a normal esterification reaction using 10% acid as a copolymerization component was melt-spun in the same manner as in Example 1 while changing the take-up speed to produce a 50 denier/24 filament polyester fiber. Obtained. Examples 2 and 3 and Comparative Example 2,
Table 2 shows the Δn, strength, elongation, and spinnability of polyester No. 3.
It is shown in Table 3.

[0025]

[Table 2]

[0026]

[Table 3]

For polymers copolymerized with adipic acid (C=6) or isophthalic acid, which are aliphatic dicarboxylic acids having less than 8 carbon atoms, the take-up speed is 5500 m/min or 6000 m/min.
When the speed exceeds m/min, the value of Δn decreases and the elongation greatly increases, resulting in yarn physical properties for ultra-high speed spinning. However, eicosanedioic acid (C= 2
0), and for those using dimer acid (C=36) as a copolymerization component, Δn ≧ at take-up speeds of 6000 m/min or higher.
0.13, indicating that both strength and elongation properties are practically sufficient, comparable to conventional drawn yarns.

Examples 4, 5 Comparative Examples 4, 5, 6 Copolymerized polyesters were prepared using 75 parts by weight of ethylene glycol, 150 parts by weight of terephthalic acid, and sebacic acid as copolymerization components, and the amounts of copolymerization were changed. Melt-spun by applying the same treatment and changing the take-up speed in the same manner,
A 50 denier/24 filament polyester fiber was obtained. Further, a 50 denier/24 filament polyester fiber was obtained in the same manner as in Example 1 except that a heating cylinder was not used. The Δn, strength, elongation, and yarn-spinning properties of the polyesters of Examples 4 and 5 and Comparative Examples 4, 5, and 6 are shown in Tables 4, 5, and 6.

[0029]

[Table 4]

[0030]

[Table 5]

[0031]

[Table 6]

In the case of Comparative Example 4 in which the copolymerized amount of sebacic acid was less than 2 mol %, the value of Δn decreased at take-up speeds of 6000 m/min or more, and the improvement effect due to copolymerization of sebacic acid was almost not achieved. Moreover, the higher the speed, the lower the spinning performance becomes. On the other hand, when the copolymerization amount of sebacic acid is 20 mol % or more, the elongation is large, the strength is not improved, and the yarn-spinning property is poor due to poor heat resistance, making it unsuitable for practical use. In addition, when a hot tube is not used, the fiber properties are high elongation and low strength, which are typical of ultra-high speed spinning, and this tendency becomes more pronounced due to the copolymerization of sebacic acid.

[0033]

[Effects of the Invention] According to the method of the present invention, even if a high-speed yarn spinning method exceeding the conventional take-up speed is adopted in the hot tube spinning method, the product properties are not deteriorated, and the strength and elongation properties are excellent. Since polyester fibers with excellent heat resistance and spinnability can be provided, productivity of polyester fibers can be significantly improved.

Claims (1)

[Claims] Claim 1: Polyethylene terephthalate, which is a copolymerized aliphatic dicarboxylic acid having 8 or more carbon atoms in an amount of 2 to 20 mol % based on the total dicarboxylic acids, is melt-spun from a spinneret, cooled once to below the glass transition temperature, and then heated. The yarn is run through a zone, and the yarn is reheated to a temperature above the glass transition temperature and below the melting point to undergo a drawing heat treatment, and at a take-up speed of 620.
A method for producing polyester fibers, which comprises taking off with a first take-off roll at a speed of 0 m/min or more.