JPH0250210B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing polyester fibers, and particularly to a method for producing polyester fibers having high strength, low elongation, and low heat shrinkage. Polyester fibers, particularly polyethylene terephthalate fibers, have many excellent properties and are therefore widely used in various applications. However, polyester fibers with higher strength, lower elongation, and low heat shrinkage are required for sewing threads, industrial fabrics, and even clothing fabrics.
However, there is no known method for efficiently producing polyester fibers that fully satisfy all of these required performances. Conventionally, as a method for producing polyester fibers with high strength, low elongation, and low heat shrinkage, for example, (1) undrawn polyester yarn is drawn at a high temperature of 120 to 180°C to a factor of 4 times or more, followed by a second drawing. The second stage is stretched to 1.1 to 1.6 times at a high temperature (150 to 220°C) higher than the first stage stretching temperature,
Furthermore, a method of limited shrinkage heat treatment at 130 to 200°C (see Japanese Patent Publication No. 42-21298), (2) tension heat treatment of the drawn polyester yarn at 150 to 250°C, and then 160 to 260°C.
and a method of relaxing heat treatment at a high temperature higher than the tension heat treatment temperature (see JP-A-52-63425), (3) 60~
A method in which stretching is started with moist heat using steam or hot water at 100°C, and before the stretching is completed, one stage of stretching heat treatment is performed with saturated steam at 110 to 150°C (Japanese Patent Application Laid-Open No. 1983-1999).
(Refer to Publication No. 73513), (4) Density in the first stage is 1.350~
Liquid bath stretched to 1.365, then 2
A method (see Japanese Patent Publication No. 47-2060) has been proposed in which the material is stretched in a steam bath so that the density becomes 1.365 or higher at each step. However, none of these methods can efficiently produce polyester fibers with high strength, low elongation, and low heat shrinkage. Can not. In other words, in method (1) above, high strength can be obtained due to the stretching at high temperature and high magnification, but on the other hand, the thermal shrinkage rate increases, and fibers with sufficiently low shrinkage cannot be obtained even with limited shrinkage treatment. . In method (2), the strength of the yarn increases at the initial stage of the tension heat treatment process, that is, at the stage of raising the temperature of the yarn, which not only deteriorates workability due to yarn breakage due to roller winding.
Energy costs are high due to the two-step heat treatment. In method (3), stretching is carried out in one stage, so not only is it difficult to achieve a high strength of 8.0 g/d or higher, but even if high strength is achieved, there will be a lot of roller wrapping, resulting in poor workability. Furthermore, since the heat treatment is performed at the same time as the stretching, fibers with low heat shrinkage cannot be obtained. In method (4), liquid bath stretching is performed, but the density is 1.350 in the first stage.
~1.365, and in order to obtain high strength due to insufficient increase in density, it is necessary to further increase the drawing ratio in the second stage, which causes deterioration of the drawing condition due to the yarn being wound around the rollers. The present invention eliminates the drawbacks of such conventional methods, allows high-magnification stretching to be carried out under good stretching conditions, and makes it possible to easily produce polyester fibers with high strength, low elongation, and low heat shrinkage. This method provides a method, the gist of which is as follows. Feed roller group for polyester unstretched tow,
In the method of performing two-stage stretching between a first draw roller group and a second draw roller group, and then heat treatment with a heating roller group, the feed roller group and the first draw roller group are heated to 35 to 55°C, and the feed roller group A hot water bath of 65 to 80℃ is provided below the final roller, and the tow is immersed at a position of 5 to 40 mm below the hot water surface for an immersion length of Z _1.
(mm) satisfies the following formula (1), the first stage is stretched between the feed roller group and the first draw roller group at a first stage stretching ratio of DR ₁ , and then the first draw roller group The second stage is drawn between the first draw roller group and the second draw roller group through a steam box with a box length Z ₂ (mm) that satisfies the following formula (2), which was installed immediately after the first draw roller group, at a second stage draw ratio of DR ₂ . Stretch, at this time
Make sure that the ratio of DR ₁ / DR ₂ satisfies the following formula (3),
A method for producing high-strength polyester fiber, which is then heat-treated with a group of heating rollers at 190 to 220°C. 12≦5√ ₁・y ₁ ≦Z ₁ ≦700 (1) 10≦2√ ₂・y ₂ ≦Z ₂ ≦600 (2) 2.0≦DR ₁ /DR ₂ ≦2.9 (3) (Here, x ₁ , x ₂ is each feed roller group,
The value obtained by multiplying the denier of 1 mm width of the tow passing through the first draw roller group by 10 ^-4 [However, x ₁ ≦ 5, x ₂
≦2.5], y ₁ and y ₂ are the speeds of the tow passing through the feed roller group and the first draw roller group (m/
min). ) Figure 1 is a schematic diagram of the stretching and heat treatment equipment used in the present invention.
7 is between the feed roller groups 1 to 7 and the first draw roller group 9 to 15, and between the first draw roller group and the second
After being stretched in two stages between the draw roller groups 16 to 22, it is heat set by the heating roller groups 23 to 26,
Sent to the next process. 8 in the figure is a hot water bath, in which the lower part of the final roller 7 of the feed roller group is immersed. Further, 28 is a steam box. The first stage stretching of the present invention is performed between the heated feed roller group and the heated first draw roller group via a warm water bath 8 in which the lower part of the final roller 7 of the feed roller group is partially immersed. The lower part of the last roller of the feed roller group is partially immersed in hot water in order to fix the drawing point of the polyester tow to the lower part of said last roller. Hot water is used as a thermal stimulus to initiate stretching. Hot water temperature is 65-80℃. At a low temperature of less than 65°C, there are many stretching points that are not fixed, resulting in unstretched parts being mixed in and yarn breakage occurring frequently. Furthermore, if the temperature exceeds 80°C, a super draw phenomenon occurs and high strength fibers cannot be obtained. Immersion length of polyester tow in a hot water bath Z ₁ (mm)
is the value of the denier per 1 mm width of the tow passing through the first draw roller group multiplied by 10 ^-4 x ₁ and the tow speed
The optimum range is determined by y ₁ (m/min).
That is, the immersion length may be determined within the range expressed by the following formula. 12≦5√ ₁・y ₁ ≦Z ₁ ≦700 (However, x ₁ ≦5) If the immersion length Z ₁ is less than 5√ ₁・y ₁ , undrawn yarn may be mixed in or yarn breakage will occur frequently. . Also, 5√
When x ₁ · y ₁ is less than 12, the fineness of the undrawn tow must be made extremely thin or the drawing speed must be extremely slow, resulting in extremely low productivity. On the other hand, if the length exceeds 700 mm, the drawing point of the tow will not be fixed under the final roller, causing frequent yarn breakage. If x ₁ >5, the thickness of the tow is too large, and uniform heating cannot be achieved, resulting in frequent yarn breakage.
This phenomenon becomes noticeable when drawing at a high magnification in order to obtain high-strength fibers. The polyester tow running from the bottom of the final roller must be kept at a position of 5 to 40 mm below the surface of the hot water. If it exceeds 40 mm, the drawing point of the tow under the final roller is shifted to the front, yarn breakage, etc. occur, and the drawing condition deteriorates. If it is less than 5 mm, the entire tow may not be immersed uniformly, which is not preferable. If the entire tow is not uniformly immersed, an auxiliary device may be used to apply hot water onto the tow. There is no problem even if hot water contains oil. When applying only thermal stimulation with hot water as described above, the tow temperature does not rise rapidly to the desired temperature;
Uneven temperature distribution tends to occur. However,
Heating the rollers of the feed roller group to 35 to 55°C has the effect of eliminating the temperature unevenness,
Fuzzing, thread breakage, etc. can be prevented, and the stretching condition will be even better. When the roller temperature is less than 35°C, no effect of heating on the stretching condition is observed. Furthermore, if the temperature exceeds 55°C, the stretching point of the tow moves from the lower part of the final roller of the feed roller in the direction opposite to the running direction of the tow and becomes unstable, resulting in poor stretching performance. The second stage stretching in the present invention is carried out using a steam box 28 provided immediately after the first draw roller group between the first draw roller group and the second draw roller group.
It is done through. In this case, the number of denier per 1 mm width of the tow passing through the first draw roller group is
The value multiplied by 10 ^-4 is x ₂ and the tow speed is y ₂ (m/min)
When the length Z ₂ (mm) of the steam box is 10≦2√ in the running direction of the polyester tow
It is necessary to satisfy x ₂ ·y ₂ ≦Z ₂ ≦600 (however, x ₂ ≦2.5). Box length Z ₂ is 2
√ ₂・y If it is less than ₂ , the tow temperature will not rise, causing thread breakage, etc. Furthermore, if 2√ ₂・y ₂ is less than 10, productivity will be extremely low. On the other hand, if it exceeds 600 mm, uniform stretching will not be possible.
Fuzz, etc. is likely to occur. When x ₂ > 2.5, the thickness of the tow is too large, making it impossible to heat it uniformly, resulting in frequent yarn breakage. Also, the roller temperature of the first draw roller group is 35 to 55℃ for the same reason as the feed roller group.
It is necessary to keep it within this range. The steam supplied to the steam box is usually saturated steam at a pressure of 0.5 to 10 kg/cm ² . Even when heated with steam, the tow temperature does not rise rapidly to the desired temperature, and uneven temperature distribution tends to occur. As an auxiliary heating means, the first
When the draw roller group is heated to 35 to 55℃, fuzz and
No thread breakage occurs and the stretching condition is good. In order to produce high-strength, low-elongation cotton, it is necessary to draw at a higher draw ratio than when producing cotton with a normal strength of 6 to 7 g/d and elongation of 30 to 35%. Furthermore, since the stretching media used in the first stage and the second stage are different between hot water and steam, the distribution of the stretching ratios in the first stage and the second stage is important. In the present invention,
The ratio of DR ₁ /DR ₂ is preferably 2.0 or more and 2.9 or less.
When the stretching ratio is less than 2.0, the stretching is mainly performed by local heating in the second stage, and therefore the stretching condition is significantly deteriorated due to non-uniform distribution of the polyester tow. Moreover, when it exceeds 2.9, the stretching in the first stage becomes the main one, and the stretching condition worsens. In the present invention, in order to stabilize physical properties such as fiber strength and elongation, and to improve fiber dimensional stability during heating, that is, to reduce heat shrinkability, heating at 190 to 220 ° C. Heat treatment is performed using a group of rollers. Heat treatment at temperatures below 190°C will result in poor dimensional stability during heating, especially when dyeing and finishing the fibers.
Heat treatment at temperatures exceeding .degree. C. increases the elongation of the fibers obtained by drawing. As described above, the polyester undrawn tow is subjected to the first stage of hot drawing between the heated feed roller group and the first draw roller group via a hot water bath, and then the first draw roller group and the second draw roller group are heated. A polyester fiber with high strength, low elongation, and low heat shrinkage is produced by a second stage of hot drawing in a steam box and further heat treatment with a group of heated rollers. It is advantageous for obtaining high-strength polyester fibers, especially those of 8.0 g/d or more. In the present invention, the polyester constituting the polyester fiber is mainly polyethylene terephthalate, but it may be copolymerized with a third component within a range that does not essentially change its properties (for example, 15 mol% or less). Examples of the third component include isophthalic acid, 5-sodium-sulfoisophthalic acid, paraoxybenzoic acid, diethylene glycol, and 1,4-butanediol. The intrinsic viscosity [η] of polyester is
0.60 or more is preferable. If it is less than 0.60, it is difficult to obtain high strength fibers. These polyesters may contain small amounts of additives such as matting agents, colorants, stabilizers, flame retardants, and moisture absorbers. The present invention makes it possible to obtain polyester fibers with high strength, low elongation, and low heat shrinkage, which could not be produced by conventionally known methods. In particular, when this staple fiber is used as a staple fiber and mixed with cotton fiber, spun yarn can be obtained with high efficiency with little yarn breakage even if the spinning spindle rotation speed is increased. Furthermore, even if the spun yarn obtained in this way is used to weave, for example, taffeta, and finished by normal methods, the shrinkage of the spun yarn on the fabric is small because the heat shrinkage rate of polyester staple fiber is low. Moreover, since localized shrinkage spots do not occur, it has the advantage that extremely high-quality products can be obtained. The present invention will be explained in more detail with reference to Examples below. In addition, the measuring method of strength, elongation, and heat shrinkage rate in Examples is as follows. Strength (g/d)/Elongation (%) When the sample is cut by fixing a constant speed loading type tensile tester: Matsukenji and pulling at a loading rate of 20 g/min so that the sample length is 20 mm. Find growth. The strength is the value obtained by dividing this tenacity value by the fineness of the single yarn determined by a conventional method. Heat shrinkage rate (%) This is the shrinkage rate when left in air at 170℃ for 20 minutes. Example 1 The intrinsic viscosity measured at 25°C using a mixed solution of phenol and tetrachloroethane (mixing ratio 1:1) as a solvent was
0.65 polyethylene terephthalate was spun using a conventional method to obtain an undrawn yarn tow of about 1.5 million denier. Next, the undrawn yarn tow was drawn using a drawing apparatus shown in FIG. The immersion depth of the tow in hot water is 10 mm, the immersion length of the tow is 300 mm, the length of the steam box is 200 mm, the temperature of the second draw roller group is 30°C, and the drawing speed (speed of the tow passing through the second draw roller). was 100 m/min, and other stretching conditions were as shown in Table 1. After stretching, the fibers were crimped by the indentation method and cut into fibers of 38 mm in length using a cutter to obtain staple fibers (raw cotton). The state of thread breakage and raw cotton properties are shown in Table 2.

【table】

【table】

[Table] There was no deterioration in drawing condition due to yarn breakage, and the raw cotton properties were also satisfactory. Comparative Example 1 Using the undrawn yarn tow and the drawing device used in Example 1, drawing was carried out under the drawing conditions shown in Table 3. The results are shown in Table 4.

【table】

【table】

[Table] In experiments No. 1 to 6, No. 9, and 10, thread breakage occurred frequently.
Stretching is not good. In experiment No. 7, the heat shrinkage rate was high;
When spun yarn was made using this raw cotton, taffeta was woven, and the yarn was finished and sorted using normal methods, the quality deteriorated due to shrinkage spots. In Experiment No. 8, raw cotton with high strength and low elongation could not be obtained. Comparative Example 2 The immersion depth of the tow in warm water, the immersion length of the tow in hot water, the length of the steam box, the thickness of the tow, and the drawing speed were changed, and the other conditions were Experiment No. 1 of Example 1.
Stretching was carried out under the same stretching conditions as shown in Table 5 using a stretching device. The results are shown in Table 6.

【table】

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of a tow stretching device used in the present invention. 1-7...Feed roller, 8...Warm water bath, 9-1
5...First draw roller, 16-22...Second draw roller, 23-26...Heating roller, 27...Tow,
28...Steambox.

Claims (1)

[Scope of Claims] 1. A method in which an unstretched polyester tow is stretched in two stages between a feed roller group, a first draw roller group, and a second draw roller group, and then heat-treated with a heating roller group.
Heat the draw roller group to 35 to 55℃, set up a 65 to 80℃ hot water bath below the last roller of the feed roller group, and place the tow at a position of 5 to 40mm below the hot water surface for an immersion length of Z ₁ (mm). is run so that the following formula (1) is satisfied, and the first stage stretching is performed between the feed roller group and the first draw roller group at a first stage stretching ratio of DR ₁ , and then the first draw roller group is installed immediately after the first draw roller group. In addition, a second stage stretching is performed at a second stage stretching ratio of DR ₂ between a first draw roller group and a second draw roller group through a steam box having a box length Z ₂ (mm) that satisfies the following formula (2),
A method for producing high-strength polyester fibers, which is characterized in that the ratio of DR ₁ /DR ₂ satisfies the following formula (3), and then heat treatment is performed using a group of heating rollers at 190 to 220°C. 12≦5√ ₁・y ₁ ≦Z ₁ ≦700 (1) 10≦2√ ₂・y ₂ ≦Z ₂ ≦600 (2) 2.0≦DR ₁ /DR ₂ ≦2.9 (3) (Here, x ₁ , x ₂ is each feed roller group,
The value obtained by multiplying the number of denier per 1 mm width of the tow passing through the first draw roller group by 10 ^-4 [however, x ₁ ≦
5, x ₂ ≦2.5], y ₁ and y ₂ represent the speed (m/min) of the tow passing through the feed roller group and the first draw roller group, respectively. )