JPH0447046B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a polyester fiber and a method for producing the same. More specifically, the present invention relates to a high-quality, homogeneous polyester fiber that has the high tenacity necessary for industrial fibers and has excellent properties such as dimensional stability and heat resistance, and a method for producing the same. (Prior Art) In general, polyester fibers are widely used as various industrial materials due to their high strength, high Young's modulus, and excellent dimensional stability, and are particularly used in tire cords, conveyor belts, V-belt cords, etc. It is preferably used as a material for reinforcing rubber structures. The most required characteristic of these industrial materials is high strength, and when used as a reinforcing material in rubber, such as in materials for reinforcing rubber structures, the vulcanization process, which is the molding process of rubber structures, is required. Because they are often exposed to high temperatures due to high-temperature processing and internal heat generation when used in final products, heat resistance is also extremely important. The problem here is that the strength decreases due to heat, and the hydrolysis reaction of polyester is significantly accelerated at high temperatures and in the presence of amines in the rubber. Conventionally, the common method for increasing fiber strength has been to increase the molecular weight of the polymer, which not only increases the strength of drawn yarn but also improves the strength utilization rate when twisted into a cord. It was hot.
For this reason, various spinning methods such as heated spinning tubes have been adopted, but when the molecular weight exceeds a certain level, the melt viscosity of the molten polymer increases, resulting in extremely poor spinnability, and the drawn yarn obtained from this is of low quality. All I could get was something. On the other hand, when the melting temperature is raised to improve spinnability, the molecular weight decreases due to thermal decomposition.
There was a problem that fibers with the desired high molecular weight could not be obtained. Looking at commercially available industrial polymer fibers, even those using relatively high molecular weight polymers have a drawn yarn strength of 9.2 to 9.3 at most.
g/d, and there are some products with a strength of around 9.5 g/d obtained by high-strength stretching in the lower molecular weight range, but because of their low molecular weight, they are used in the twisting process and dip treatment process, for example, as rubber reinforcing materials. There was a problem in that the strength decreased significantly over time. On the other hand, regarding heat resistance, it is necessary to suppress the hydrolysis peculiar to polyester, and in addition to polymer modification such as low carboxylation, differences in fiber structure due to differences in yarn spinning methods also have a large influence. That is, it is preferable to have a homogeneous fiber with a small difference between crystalline and amorphous, which has a high degree of crystallinity as a fiber structure and has a strong structure by increasing the orientation of the amorphous portion. (Problems to be Solved by the Invention) An object of the present invention is to provide a homogeneous industrial polyester fiber that has high strength and improved heat resistance, and further uses a high molecular weight polymer to The object of the present invention is to provide a method for producing a homogeneous industrial polyester fiber having high strength and improved heat resistance. (Means for Solving the Problems) The present inventors investigated the surface shapes of various polyester fibers after undergoing various chemical treatments, and found that under certain conditions, ethylamine treatment was performed. It was discovered that the surface condition after the formation has an extremely good correlation with strength and heat resistance, and by specifying this surface shape, it was possible to produce industrial polyester fibers with high strength and improved heat resistance. The present invention was achieved by discovering that the present invention can be obtained. That is, the first invention of the present invention is a drawn fiber obtained by uniformly drawing a low-oriented undrawn yarn with a birefringence of 250×10 ^-5 or less by slow cooling after spinning a high-viscosity polymer at a high magnification. Consisting of thread with intrinsic viscosity of 0.92 or more, birefringence
0.19 or higher, and the fibers are dissolved in a 60% by weight aqueous solution of ethylamine in a sealed tube at 30℃ for 20 minutes.
After being soaked for an hour, then washed with water and ethyl alcohol, air-dried, and observed under an electron microscope at 500x magnification, the surface of the fibers was found to have no irregular cracks and to be perpendicular to the fiber axis direction. A polyester fiber characterized by having an average number of directional cracks of 5 or less per 200 μm of fiber length. Furthermore, the second invention of the present invention has a material having an intrinsic viscosity of 0.95 that contains ethylene terephthalate as a main repeating unit.
Melting temperature of molten polyester over 280~300
℃ and supplied to a gear pump, which increases the pressure to 400 to 1200 Kg/cm ² G and supplies it to a spinning pack, and then spins out from a spinneret into a heating zone of 340℃ or higher. , after cooling and solidifying,
Birefringence decreases by pulling at a speed of 300 to 700 m/min.
This method of producing polyester fibers is characterized in that an undrawn yarn of 250×10 ^-5 or less is obtained, and then heated steam is injected and at the same time the yarn is drawn four times or more. Conventionally, X-ray diffraction rate is often used as a means of investigating fiber structure, but even when there is no primary correlation between X-ray diffraction and fiber physical properties, for example, the hydrolysis resistance of fibers may change. These facts suggest that it is necessary to consider fine structures other than ultra-microns. Many attempts have been made to elucidate the fine structure of polymer solids by taking advantage of their high sensitivity to solvolysis reactions. For example, if the crystalline and amorphous portions on the fiber surface can be selectively etched, it is possible to directly determine the fine structure. 1 of these
One method is to treat polyester with amines, etc., and observe its surface condition using an electron microscope (Abe, Sakamoto, Kobunshi Ronsen, 35 , 587-593).
(1978), Abe, Sakamoto, Kobunshi Papers, 33 , 263~
269 (1976). The present researchers further examined these methods from various angles and found that by selecting the treatment conditions with amines, it is possible to very accurately relate the surface condition of fibers to predetermined properties. Ta. The optimum treatment conditions for industrial polyester fibers in the present invention include immersion in a 60% by weight aqueous solution of ethylamine in a sealed tube at 30°C for 20 hours. If the processing conditions are inappropriate, such as the concentration of ethylamine, the processing temperature, or the processing time is too large or too small,
The desired selective etching is not achieved. After the ethylamine treatment, water washing and ethyl alcohol washing are performed, followed by air drying. As described above, when polyester fibers are treated with ethylamine, the surface of the polyester fibers is selectively etched, and
Clear cracks can be observed on the surface of the fibers in the enlarged photo. The conditions of cracks are diverse, and the direction and number of cracks are greatly influenced by the spinning conditions. To explain the content of cracks below, firstly, an irregular crack refers to a crack in a direction other than the fiber axis direction or a direction perpendicular to the fiber axis, and the absence of irregular cracks means that the crack is substantially in the fiber axis direction. and perpendicular to the fiber axis. Fig. 1 shows an example without irregular cracks, and Fig. 2 shows an example with irregular cracks. Next, regarding the counting of cracks in the direction perpendicular to the fiber axis direction, only those that can be observed on the photograph are counted; A crack within 200 μm of the direction shall be counted as one crack.
That is, in FIG. 3A, it is counted as 5 pieces, and in FIG. 3B, it is counted as 4 pieces. The presence or absence of these irregular cracks and the number of cracks are important characteristics when polyester fiber is used as a material for reinforcing rubber structures. It shows an extremely good relationship with the residual strength (heat-resistant strength) after being embedded in rubber and vulcanized at high temperatures. Figure 4 shows the correspondence between the treated code strength and heat resistance strength, the number of cracks, and the presence or absence of irregular cracks.As the number of cracks decreases, the treated code strength and
It has been shown that the heat resistance strength is improved, and that the presence or absence of irregular cracks has a significant effect on the heat resistance strength, and that those without irregular cracks have higher heat resistance strength. In this way, it can be said that creating a structure that is resistant to attack by amines, with no irregular cracks and a small number of cracks in the amine treatment, brings about high strength and high heat resistance, which is preferable as a fiber for reinforcing rubber structures. The surface shape of the polyester fiber of the present invention after ethylamine treatment has no irregular cracks, and the number of cracks in the direction perpendicular to the fiber axis is on average 5 or less per 200 μm of fiber length. The polyester fiber of the present invention has high strength and excellent heat resistance, and is extremely useful as an industrial fiber. The polyester used in the present invention refers to any polymeric polyester obtained from α-ω-glycol and dicarboxylic acid, particularly any polymeric polyester obtained from polymethylene glycol and aromatic dicarboxylic acid. Among these, the most representative one is polyethylene terephthalate obtained from ethylene glycol and terephthalic acid. The intrinsic viscosity of the polyester fiber of the present invention is 0.92 or more, preferably 0.93 or more. Intrinsic viscosity is 0.92
Below this, sufficient strength and heat resistance cannot be maintained in terms of strength retention during dip treatment, hydrolysis resistance in rubber, and amine decomposition resistance. On the other hand, the concentration of unterminated carboxyl group is 15 equivalent/10 ⁶
It is desirable that the amount be less than gram. If it exceeds 15 equivalents/10 ⁶ grams, the chemical stability will be insufficient, and the heat resistance will be particularly poor. Various known methods can be used to lower the carboxyl group. For example, (1) a method in which phenyl glycidyl ether is reacted with a molten polyester as disclosed in Japanese Patent Publication No. 44-27911, and (2) a method in which a linear polyester carbonate is reacted with a molten polyester as in Japanese Patent Publication No. 45-41235. Method (3) A method of reacting polyester with ethylene oxide as in Japanese Patent Publication No. 47-12891 (4) A method of reacting polyester with glycol ester of oxalic acid or oxalic acid polyester as in Japanese Patent Publication No. 48-35953 (5) ) Method of reacting polyester with cyclic carbonate as disclosed in Japanese Patent Publication No. 48-41713 (6) Reacting polyester with diaryl oxalates and/or diaryl malonates and diaryl carbonates as disclosed in Japanese Patent Publication No. 49-5233 (7) Method of reacting carbodiimide with polyester as in U.S. Pat. No. 3,193,522. (8) Method of reacting biscyclic imino ether as in JP-A-55-145734, etc. to obtain desired intrinsic viscosity and unterminated carboxyl groups. It can be adopted at any time depending on the quantity. In particular, it is preferable to avoid coloring of the resulting molded product, avoid foaming due to decomposition of additives during molding, and reduce the amount of unterminated carboxyl groups to 15 equivalents/10 ⁶ grams or less without reducing the degree of polymerization. It is. Furthermore, in order to provide the polyester fiber of the present invention with sufficient strength and heat resistance, it is essential to increase the degree of orientation of the amorphous portion, and the birefringence must be 0.19 or more. This is primarily to achieve the desired high strength, but at the same time, in addition to improving chemical stability due to the aforementioned low carboxylization,
This is to stabilize the structure by increasing the orientation of the amorphous portion, and the mutual effect of the two makes it possible to dramatically improve heat resistance. If the birefringence does not reach 0.19, a material with insufficient strength and heat resistance will be obtained. Next, the method for producing polyester fibers of the present invention will be described. A high molecular weight molten polyester having an intrinsic viscosity of 0.95 or more, preferably 0.98 or more is maintained at a relatively low melting temperature of 280 to 300°C, preferably 280 to 290°C, and is supplied to a gear pump, and further by the gear pump.
A high pressure of 400 to 1200 kg/cm ² G is supplied to the spinning pack and the subsequent spinneret. Melting temperature is 280
If the temperature is below ℃, the viscosity of the polymer discharged from the spinneret is too high, resulting in problems with the uniformity of the undrawn yarn, which may cause yarn breakage during the drawing process.
On the other hand, if the melting temperature is set to 300℃ or higher, the residence time at high temperature until discharge from the spinneret becomes longer.
A drawn yarn with the desired high molecular weight cannot be obtained. Additionally, pressure losses in the gear pump, spin pack, and spinneret have similar effects. That is, 400-1200Kg/ ^cm2
The pressure drop in G provides the optimum spinning temperature for spinning high molecular weight polymers without causing excessive molecular weight loss. The polymer temperature in the spinneret section is in the range of 310-330°C. The polymer discharged from the spinneret passes through a high-temperature heating zone, and then is cooled and solidified in a cooling device. The heating zone is 200 to 500 mm long, and the air temperature near the surface is
It is a cylindrical heater designed to reach a temperature of 340℃ or higher. This heating zone maintains the heat of the spinneret surface, maintains the ejected high intrinsic viscosity yarn at a high temperature and delays cooling, thereby lowering the spinning tension and lowering the degree of orientation of the resulting undrawn yarn. The cooling device may be of any shape as long as it can uniformly cool the yarn. The cooled and solidified yarn is oiled by a conventional oiling device, taken off at a relatively low speed, and then fed to a drawing process. It is advantageous to set the take-off speed as low as possible in order to suppress crystallization of the undrawn yarn and reduce the degree of orientation, but taking productivity into account, it is preferably set at 300 to 700 m/min. As mentioned above, the melting temperature is lower (280 to 300
°C), pressure loss during normal melt spinning (pack pressure)
High pressure drop (400-1200Kg/cm ² G) compared to
Heating at relatively high temperatures in the heating zone under the mouthpiece (340
℃ or higher), and relatively low speed pick-up (300℃ or higher)
700 m/min), the high molecular weight polyester can be spun stably, has a high intrinsic viscosity, and has a low degree of orientation (250×10 ^-5 or less in terms of birefringence) that can withstand high-magnification stretching. )
It is possible to obtain homogeneous undrawn yarn, which is the first important point for obtaining the polyester fiber of the present invention. The second point to obtain the polyester fiber of the present invention is to uniformly draw the undrawn yarn obtained by the above method at a high magnification, and for this purpose, heated steam is injected and at the same time the yarn is drawn four times or more. Adopt a method. For heated steam stretching, a heated steam injection device is placed between the drawing rollers, and heated steam is injected onto the undrawn yarn to raise the yarn temperature to above the glass transition point at once, and the drawing point is fixed near the heated steam injection point. Stretching is performed by a factor of 4 or more between the rollers. The heated steam injection device may be of any shape as long as it can uniformly inject heated steam onto the yarn. For example, there is an injection device equipped with a slit of 1 to 5 mm, which has a closed structure except for the thread passage section in order to improve thermal efficiency. The heating steam preferably has a temperature of 350 to 550°C and a pressure of 1.5 to 10 kg/cm ² G. If the temperature is less than 350℃ and the pressure is less than 1.5Kg/ ^cm2 , the amount of heat for uniform stretching is insufficient; if the temperature exceeds 550℃ and the pressure is more than 10Kg/ ^cm2 , the amount of heat will be excessive and the yarn will be stretched. Fusion etc. occur. Following the drawing with heated steam, the yarn is advanced to a heat treatment device consisting of heated rollers, etc. However, during the drawing with heated steam, it is also subjected to considerable heat treatment at the same time, so excessive heat treatment is unnecessary, and the temperature of the heated roller is 150-220°C is sufficient. By such high magnification and uniform stretching, extremely highly oriented polyester fibers with birefringence of 0.190 or more can be obtained. If the degree of orientation is less than 0.190, the heat resistance will be poor. Regarding the correspondence between the above manufacturing method and the surface shape of the obtained polyester fiber after ethylamine treatment, it is found that due to the combined effect of the melt spinning method and the drawing method of the present invention, the polyester fiber has no irregular cracks and has a small number of cracks. However, it is presumed that the melt spinning method is effective in reducing the number of cracks, and the high magnification and uniform stretching is effective in suppressing irregular cracks. Although the above-mentioned direct spinning and drawing method is most suitable as the spinning method for the present invention, it is not a problem even if the spinning and drawing are carried out separately. Furthermore, as for the stretching method, the effect is most remarkable in one-stage stretching, but
A stretching method with more than tiers is also possible. The polyester fiber obtained by the present invention, that is, the polyester fiber obtained by melting high molecular weight polyester at a low temperature, spinning it through high pressure loss, and drawing it using heated steam, has no irregular cracks in its surface shape when treated with ethylamine. , the number of cracks in the direction perpendicular to the fiber axis is less than 5 on average per 200 μm of fiber length, which is a feature not found in conventional polyester fibers. Furthermore, we evaluated the general physical properties of these polyester fibers as industrial fibers, and found that the drawn yarn strength, raw cord strength, treated cord strength,
It was found that the strength after high-temperature vulcanization (180℃) is extremely superior compared to conventional polyester fibers. These evaluation results indicate that the polyester fiber of the present invention is optimal for industrial use, particularly as a fiber for reinforcing rubber structures. (Example) The present invention will be explained in more detail with reference to Examples below. Note that the intrinsic viscosity in the present invention was measured in an orthochlorophenol solution at 35°C, and the concentration of unterminated carboxyl groups was determined by Econics (A.
Conix) method (Makromol.Chem. 26 , 226,
(1958)). Birefringence was measured using a polarizing microscope using bromnaphthalene as an immersion liquid and a retardation method using a Bereck compensator. Example 1 Polyethylene terephthalate chips having an intrinsic viscosity of 1.1 were melted, the melt temperature was maintained at 285° C., the melt was supplied to a gear pump, passed through a spinning pack, and then spun from a spinneret. At this time, an ordinary wire mesh filter and sand were inserted into the spinning pack to increase the pressure and filter the polymer. The pressure of the polymer just before the spinning pack is 800Kg/cm ² G, and the temperature of the polymer is
It was 315℃. In addition, the spinneret has pores with a diameter of 0.5 mm.
It consisted of 250 pieces, and the discharge amount was 20.2 kg/hour. The discharged yarn is heated in the normal heating zone,
The film was passed through a cooling device, subjected to an oiling treatment, then wound around a supply roller, and further stretched 6 times by spraying heated steam between it and a stretching roller, passed through a cooling roller, and wound up at 2000 m/min. heating steam is temperature
The temperature was 400°C, the pressure was 3 Kg/cm ² G, and the temperature of the stretching roller was 160°C. The obtained drawn yarn had a denier of 1500 and an intrinsic viscosity of 0.96. After this drawn yarn was subjected to ethylamine treatment (60% aqueous solution, 30℃, 20 hours), it was examined using an electron microscope.
When the surface condition was observed under 500 times magnification, the cracks on the surface were regular and few in number.
That is, the number of cracks perpendicular to the fiber axis direction was 0.5 per 200 μm, and the cracks in the fiber axis direction were regular. In addition, the physical properties of the drawn yarn before ethylamine treatment are
9.6g/d, elongation 14.5%, and the raw cord made by twisting two of these drawn yarns together to a size of 40S x 40ZT/10cm is treated with a normal adhesive.
It was found to be extremely superior to conventional polyester fibers, with a strength of 25.2 kg and an elongation of 19.5%. Furthermore, this treated cord was embedded in unvulcanized rubber and vulcanized at 170℃ for 120 minutes (press pressure 50Kg/
cm ² ), the cord was taken out and its residual strength was measured, and it was found that it maintained an extremely high level of strength (see Table 1). Example 2 Melt-spinning direct stretching was carried out in the same manner as in Example 1 using polyethylene terephthalate chips having an intrinsic viscosity of 0.98. The melting temperature is the same 285℃,
Before spinning the polymer, the pressure is 600Kg/cm ² and the temperature is
It was 310℃. Stretching was carried out in the same manner as in Example 1 using heated steam at 400° C. and 3 Kg/cm ² . The surface condition in the electron micrograph of the obtained drawn yarn after ethylamine treatment shows that cracks are regular, and the number of cracks perpendicular to the fiber axis direction is 200μ.
It was 2.0 pieces per m. In addition, the strength of drawn yarn, raw cord, and treated cord,
The elongation and strength retention after high temperature vulcanization also showed good levels (see Table 1). Example 3 Melt-spinning direct stretching was carried out in the same manner as in Example 1. At this time, the discharge rate was adjusted and the stretching speed was set at 2500 m/min. The melting temperature is
285℃, polymer pressure 500Kg/cm ² before spinning pack,
The temperature was 318℃. The surface shape of the obtained drawn yarn after the ethylamine treatment was good, and the performance of the treated cord was also excellent (see Table 1). Comparative Example 1 Melt spinning was carried out in the same process as in Example 1 using polyethylene terephthalate chips having an intrinsic viscosity of 1.1. Here, the melting temperature is 310℃, the temperature of the polymer just before the spinning pack is 317℃, and the pressure is
It was 200Kg/ ^cm2 . Following spinning, the fiber was stretched 6.0 times using a heated roller. This stretching was carried out in two stages by adjusting the temperature of the heating roller from 70 to 140°C. Here, the heating roller temperature in the first stage was 80°C, and the heating roller temperature in the second stage was 120°C. The temperature of the second stage stretching roller was 180°C. After the obtained drawn yarn was treated with ethylamine in the same manner as in Example 1, the surface condition in an electron micrograph was observed, and the cracks were extremely irregular.
And the number was extremely large. In addition, the strength and elongation of the drawn yarn, raw cord, and treated cord, as well as the residual strength indicating vulcanization resistance, were at very low levels (see Table 1). Comparative Example 2 Melt spinning was carried out in the same manner as in Comparative Example 1, and the same heated steam stretching as in Example 1 was carried out. An electron micrograph of the obtained drawn yarn after ethylamine treatment shows more regular cracks than in Comparative Example 1, but
On average, 8.5 cracks perpendicular to the fiber axis were observed per m. As shown in Table 1, the strength, elongation, and vulcanization resistance of this drawn yarn, raw cord, and treated cord are improved compared to Comparative Example 1, but are considerably inferior when compared with those of the present invention. . Comparative Example 3 Using polyethylene terephthalate chips with an intrinsic viscosity of 1.1, melt spinning was carried out under the conditions of a melting temperature of 305°C, a polymer temperature of 314°C immediately before spinning pack, and a pressure of 320 kg/cm ² G, followed by heated steam stretching. The surface shape of the obtained drawn yarn after ethylamine treatment showed regular cracks, but the number of cracks in the direction perpendicular to the fiber axis was 6.0 per 200 μm of fiber length. Furthermore, as shown in Table 1, the strength of the drawn yarn, the strength of the cord, and the strength after high-temperature vulcanization were all inferior to those of the present invention. Comparative Example 4 After melt spinning in the same manner as in Example 1, direct stretching was performed in the same manner as in Comparative Example 1. The surface shape of the obtained drawn yarn after the ethylamine treatment had irregular cracks, and the number of cracks in the direction perpendicular to the fiber axis was 7.0 per 200 μm.
Moreover, the code performance was also inferior compared to that of the present invention (see Table 1).

[Table] (Effects of the invention) The polyester fiber according to the present invention has extremely high strength and excellent heat resistance, whereas conventional polyester fiber was limited to the field of small cars such as passenger cars as tire cord. As a result, it can be used in medium and large vehicles such as light trucks, trucks, and buses, and a significant expansion of applications is expected.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the surface shape of fibers treated with ethylamine (example without irregular cracks);
The figure is a schematic diagram showing the surface shape of fibers (irregular cracks) due to ethylamine treatment. Figure 3 is a schematic diagram showing the fiber surface shape to explain how to count cracks. Figure 4 is the number of cracks and treatment code strength. , is a graph showing the relationship between heat resistance and strength.

Claims (1)

[Scope of Claims] 1 Consisting of a drawn yarn obtained by spinning a high viscosity polymer, followed by delayed cooling and uniformly drawing a low oriented undrawn yarn with a birefringence of 250×10 ^-5 or less at a high magnification. A polyester fiber with an intrinsic viscosity of 0.92 or more and a birefringence of 0.19 or more, which is treated with ethylamine in a sealed tube.
It was immersed in a 60% by weight aqueous solution at 30°C for 20 hours, then washed with water and ethyl alcohol, air-dried, and observed under an electron microscope at 500x magnification.
There are no irregular cracks on the fiber surface, and the number of regular cracks in the direction perpendicular to the fiber axis is determined by the fiber length.
A polyester fiber characterized by having an average of 5 or less fibers per 200 μm. 2. The polyester fiber according to claim 1, wherein the terminal carboxyl group concentration is 15 equivalents/10 ⁶ grams or less. 3. The polyester fiber according to claim 1 or 2, wherein the polyester fiber is made of polyester having ethylene terephthalate as a main repeating unit. 4 Melt polyester with an intrinsic viscosity of 0.95 or more,
It is maintained at a melting temperature of 280-300℃ and supplied to a gear pump, which increases the pressure to 400-1200Kg/
cm ² G and fed to the spinning bag, then spun from the spinneret into a heating zone of 340°C or higher, cooled,
After solidification, the yarn is drawn at a speed of 300 to 700 m/min to obtain an undrawn yarn with a birefringence of 250 x 10 ^-5 or less, and then stretched to 4 times or more while injecting heated steam. A method for producing polyester fiber according to claim 1. 5. The method for producing a polyester fiber according to claim 4, wherein the polyester has ethylene terephthalate as a main repeating unit.