JPS6024852B2 - Manufacturing method for high modulus and high strength fibers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing high modulus, high strength fibers, and more particularly, to a method for producing novel high modulus, high strength fibers, and more particularly to amorphous or as low as possible crystalline raw materials made of known polymers. The present invention relates to the production of novel high-strength, high-strength fibers having a structure very similar to fully stretched truncated crystals by zone drawing and zone heat treatment of the fibers.

In recent years, research on the production of high modulus and high strength fibers has become very active.

These studies can be broadly divided into research on the search for new polymers and research on higher-order structure rearrangement of general-purpose polymers.
For the former, Keviar fibers (e.g., U.S. Pat. No. 3,671,542; U.S. Pat. No. 3,6
A typical example of this is the development of Polymers (No. 00, No. 35, etc.), but although there are reports on the synthesis of a wide variety of other polymers, there are problems in terms of raw material costs,
Since many requirements must be met, such as the need for outstanding properties and the availability of demand, the probability of successful industrialization is extremely small. On the other hand, for the latter, high-pressure extrusion molding (
For example, Journal of Polymer Science, Polymer Physics Edition (J.PoMm.Sci.
, Polym. phys. Ed. ) 12,635 [19
74], etc.), high-speed spinning (e.g. Origaku Journal, 33, T-
208 [1977]), high pressure crystallization (e.g. Polymer (poIMmer), 14,463 [1973]), ultra-stretching (e.g. Journal of Polymer Science,
Polymer Physics Edition (J. Polym.
Sci, Polym. Sh. Ed. )1311770
975] and Journal of Polymer Science,
Polymer Physics Edition (J. Polym.
SCi, PoIMm. PhyS. Ed. )15,142
7 [1977], etc.), frozen paper yarn (for example, Tsubaki Kimiaki 51
-6241 Publication) "Highly elastic hard fibers (for example, Journal of Macromolecular Science Physics (
J. N is croml. Sci. -Phys. )B5,7
2 [1971]), highly elastic hard coatings (e.g. ACS Polymer Preprint (ACS), Polymer
Preprints) 14, 88 268 [1973]
) and flash spinning (for example, "Molecular Design of Polymers" edited by the Society of Polymer Science, Tofukan [1972] p. 12), and many other studies have been reported.

However, there are many problems with industrialization and product quality, and the current goal is not fully achieved.

For example, even if it has already been produced on an industrial scale, flash paper yarns only yield short fibers, and high-speed weaving yarns have low crystallinity due to the rapid cooling of the molten material, making the quality seem to be one step further. In addition, high-pressure crystallization can only obtain a bulk that can be observed with an electron microscope and has no practical value. In the field of high elastic modulus and high strength fibers, the present inventors conducted intensive research to obtain fully extended chain crystals based on a new idea, and in the process, the obtained fibers It was found to have extremely excellent mechanical properties, and it became clear that parenthesis-like fibers could be obtained quite easily.
This has led to the completion of the present invention.

That is, the present invention involves stretching an amorphous or as low-crystalline thermoplastic synthetic fiber as possible through a short heating zone while locally heating it from the surroundings at a temperature from its glass transition point to its crystallization temperature. The fibers are drawn downward to form amorphous or low-crystalline highly oriented fibers, and then subjected to zone heat treatment, where the fibers obtained above are subjected to short heat treatment at a temperature above the crystallization temperature while applying high tension to fully extend the molecular chains. This is a method for producing high-modulus, high-strength fibers that is characterized by passing through the tropics and locally heat-treating them from the surrounding area.

Since the present invention is configured in this way, the effects of stretching and heat treatment can be sufficiently achieved with extremely low energy. That is, stretching can be carried out quickly and easily without distortion by causing necking with very little energy due to the zone, and preheating and heating crystallization can be performed using very little energy due to the heat treatment due to the zone. Moreover, since the heating time is short, it is advantageous in terms of preventing thermal decomposition of the fiber itself. Furthermore, the present invention has various advantages such as a simple device and very easy operation. Taking all of these advantages into consideration, it can be said that the present invention is an extremely superior industrial method for producing high elastic modulus and high strength fibers. The following points are significant differences between the method of the present invention having the above structure and the conventional method for producing high-modulus, high-strength fibers.

'1- Methods such as high-speed paper yarn, frozen paper yarn, and flash spinning attempt to obtain an extended chain structure, but the resulting fibers have a non-equilibrium, amorphous structure and are different. However, the method of the present invention can form a sufficiently stable crystal structure. '2' In methods such as high-pressure extrusion and high-pressure paper thread, high pressure is applied to the raw material side, and the tensile force applied to the product side is auxiliary, and molecular chains are expected to be oriented by the shearing force near the beginning of the grade thread. There is a danger that the molecular chains will become stuck in a "lint-like" state near the mouthpiece.

On the other hand, since the method of the present invention utilizes only tensile force, it is difficult for the molecular chain to assume any conformation other than fully extended. [31 Other methods attempt to directly complete the desired structure from the melt to form fibers or films, but the method of the present invention attempts to accomplish this through secondary processing at a lower temperature. be.

Hereinafter, each of the requirements constituting the present invention will be explained.

The fibrils used in the present invention are preferably amorphous fibers that do not contain existing crystals, such as lamellae, but if these are not available, low-crystalline non-oriented fibers can also be used. The orientation and crystallinity of the fibrils used in the present invention are polyethylene tyrephthalate, with a birefringence of 0.3 x 10-3 and a crystallinity of 1.8% by density method. 6, the birefringence is 0.5×10-3, and the crystallinity by density method is 27.7%. Such fibers usually correspond to the fibers of asp blood. The fineness, outer diameter, and other shapes of the fibers used in the present invention are not particularly limited. According to the findings of the present inventors, the material of the fibrils used in the present invention may include crystalline polymers such as polypropylene and polyethylene in addition to polyethylene terephthalate and nylon 6. In the present invention, zone drawing is first applied to the fibril.

The purpose of this zone stretching is to prevent the crystallization of the fibrils as much as possible and to align the molecular chains and aggregate them in an eastern shape.
In other words, the aim is to obtain fibers with as low crystallinity as possible and with high orientation. According to the zone drawing of the present invention, the fibrils are not only drawn very easily and quickly while causing netting, but also uniformly drawn without distortion. The zone stretching of the present invention can be carried out in a very simple apparatus as shown in FIG.

In FIG. 1, only one ring-shaped heating furnace or band heater 2 with two ribs in width is fixedly attached to a movable crosshead 1. This heating furnace is equipped with a voltage regulator (
(not shown) so that the temperature of the furnace 2 can be maintained constant. On the other hand, the upper end of the fibril 3 is fixed to a holder 4, and its lower end is also fixed by a chuck 5, and its position is determined by twills 6 and 7. Further, the lower end of the fibril is configured such that an arbitrary high tension is applied to the fibril by a load (not shown). Further, the heating ring-shaped heating furnace 2 can be moved vertically along the fiber axis, and its moving speed is as follows.
For example, one of speeds such as 2, 4, 8, 10, 20, and 40/min can be selected. The apparatus shown in FIG. 1 is the simplest example in which one ring-shaped heating furnace is applied, but when carrying out the present invention, it is not necessary to use only one ring-shaped heating furnace, but rather a plurality of ring-shaped heating furnaces. Of course you can also use it.

Similarly, the shape of the heating furnace is not limited to a ring shape, but various shapes such as a U-shape or a D-shape can be used, and the width (thickness) of the heating furnace can be changed depending on the moving speed. ) can be selected arbitrarily. In a case where a plurality of furnaces are used, it is particularly effective to install a cooling device (for example, an air cooling device or a water cooling device) between the upper and lower sides of the furnace. On the other hand, although Fig. 1 shows the simplest case 1, the fibrils themselves to be processed can be processed in various forms, such as by arranging multiple fibrils in a straight line or in a ring. It is possible. As described above, the present invention can be implemented in various forms without changing the technical idea of the present invention. Generally, zone drawing is carried out by moving the ring-shaped heating furnace 2 upward from the lower end of the fibril.

The temperature applied during zone drawing varies depending on the material, form, tension, furnace movement speed, etc. of the fibril, but in the present invention, the fibers after zone drawing should be as highly oriented and as low in crystallinity as possible. This is determined with consideration given to reducing distortion.

The present inventors applied a temperature higher than the glass transition temperature and lower than the crystallization temperature in view of the fact that it is necessary to draw at a temperature substantially below the crystallization temperature of the fibril. However, depending on the moving speed of the furnace, the temperature may be higher than the crystallization temperature. As mentioned above, it is necessary to improve the orientation of the molecular chains as much as possible during the zone stretching process, but if the temperature of the zone stretching is too high, crystallization will occur, which is not appropriate. The speed of movement of the furnace during zone stretching,
The tension is appropriately selected so that the fibers after zone stretching are as highly oriented and amorphous as possible, and have less distortion.
In this case, the preferred tension should be selected in relation to the material, the zone drawing temperature, and the moving speed of the furnace; for example, if the tension is too high, it may lead to whitening due to destruction of the structure. There is a feeling of sympathy. In addition, a multi-stage zone stretching method is also an effective method, and methods such as ■-method in which the tension is increased sequentially at a constant temperature, ■-method in which the temperature is sequentially increased while the tension is constant, and ■method in which both temperature and tension are increased are also applicable. can. The fibers zone-drawn in this manner still have low crystallinity and high orientation at this stage.

In such a state, the mechanical properties such as Young's modulus and breaking strength are still 4.0 times lower than those to which the following zone heat treatment is applied. Zone drawn fibers require subsequent zone heat treatment.

This zone heat treatment is a treatment for suppressing the formation of lamellar crystals and constructing the entire fiber with extended chain crystals. As the device used for the zone heat treatment, the same device as that used in the zone stretching can be used.

When applying the apparatus shown in Figure 1, the ring-shaped heating furnace 2 is kept at a constant temperature, and the heating furnace is moved from one end of the sample 3 at a constant speed. That is, while slowly moving the ring-shaped heating furnace, cut chain crystals extending from one end of the sample are sequentially formed. At this time, the molecular chains of the fibers are gradually aligned and crystallized in an eastern shape. In such a zone heat treatment, the heated portion is softened and the total tension acts intensively, so that oriented crystallization proceeds more effectively. This also leads to advantages such as preventing the occurrence of multiple crystal nuclei, eliminating internal distortion of the crystal, and eliminating thermal deterioration since heating is not performed for a long time. The direction of movement of the ring-shaped heating furnace mentioned above is from the bottom to the top while the sample is elongating due to heat treatment, but it can be moved from either direction as long as the dimensions are stable. Even if carried out, the processes of preheating, heating Komakichi crystallization, and cooling can be accomplished at once by moving the furnace. Zone heat treatment needs to be carried out at a higher temperature and under higher tension than in zone stretching.

The temperature of the zone heat treatment varies depending on the material, form, tension, furnace moving speed, etc. of the fibril, but is at least the crystallization temperature, preferably at least the crystallization temperature and close to the melting point. When attempting to obtain fibers with better physical properties, the temperature can be set near the maximum Young's modulus as described later, as one measure. If the heat treatment temperature is not appropriate and is too high, not only will the Young's modulus decrease, but the fibers will gradually turn white and be cut. This is probably due to distortion and local breakage occurring in the fibers. As is easily understood from the above, the zone heat treatment can be carried out in a very short time such as one minute.

Further, zone heat treatment can also be carried out in a multi-stage manner, similar to zone stretching, so that the time can be further shortened and the effect can be increased. The tension during zone heat treatment needs to be higher (higher tension) than in zone stretching, and if you want to obtain a better property, the tension should be lowered as well as the zone heat treatment temperature. It can be set near the maximum Young's modulus of the obtained fiber.

If the tension is too high, distortion or local breakage will occur in the fibers, similar to the heat treatment overload. Tension during heat treatment is the folding of molecular chains
In particular, in the case of zone heat treatment, it is easy to form a highly oriented, highly crystalline east-shaped fiber structure despite the narrow heating zone and short heat treatment time, and to easily produce fibers that exhibit high elastic modulus and high strength. This can be said to be an important requirement for manufacturing.
Regarding the number of times of zone heat treatment, the results obtained using the apparatus shown in Figure 1 indicate that one time is insufficient, and at least three times.
times were necessary.

After 3 times or more, the value gradually became constant, and about 5 times showed the optimum result.

As can be understood from the above description, in the method of the present invention, zone stretching and zone heat treatment can be performed continuously in one apparatus.

That is, a plurality of ring-shaped heating furnaces or band heaters are provided at predetermined intervals, and the temperature of each heating furnace or band heater is set to a temperature suitable for zone stretching and a temperature suitable for zone heat treatment, and the tension of each is set at a temperature appropriate for zone stretching and zone heat treatment. Zone stretching and zone heat treatment can be carried out sequentially by control using conventional means. On this occasion,
As mentioned above, inserting a cooling device between the furnaces will further increase the effect. This applies equally to vertical machines as well as to the horizontal machines shown in the zone drawing machine. The fibers obtained in this way show very interesting results, both in terms of microstructure and in terms of mechanical properties.

Regarding the microstructure of the obtained fibers, the birefringence and crystallinity of the fibers obtained according to the present invention are higher than many conventionally reported values, and can be said to be in a very highly oriented state and a highly fed crystal state.

That is, the birefringence and crystallinity of polyethylene terephthalate reach 0.247 and 60%, as shown in the examples below, and the birefringence and crystallinity of nylon 6 are 0.062. and reaches 48.9%. Judging from the meridional interference of small-angle x-ray diffraction, the crystal structure of the fiber obtained by the present invention shows that the main body of the crystal structure is extended chain crystals, although some lamellae are observed. The aggregation state of molecular chains in the amorphous region of the fiber obtained by the present invention can be said to be in a highly tensile and constrained state from the results of measurements of dynamic viscoelasticity, creep, and thermal contraction. That is, in the case of the fiber obtained by the present invention, for example, in the case of polyethylene terephthalate, there is no creep at all up to 200°C and the heat shrinkage is only about 4%. It is thought that the molecular chains in the amorphous region are fully extended and form a densely packed bundle-like aggregation. As is clear from the above explanation, the microstructure of the fibers obtained by the present invention is considered to be essentially a tufted micelle structure consisting of almost perfectly oriented east-shaped crystals and fully extended amorphous chains. It will be done.

Regarding the mechanical properties of the fibers obtained, the Young's modulus of the fibers obtained according to the invention is significantly higher compared to fibers heat-treated by other methods.

For example, the Young's modulus of zone heat-treated polyethylene terephthanot fiber is 18 x 1 and od e/, which is equivalent to the polyethylene terephthanote crystalline modulus value of 107.8 x
It corresponds to 1/6 of 1 and od skin e/. The Young's modulus of zone heat-treated nylon 6 is considerably lower than the crystalline modulus of nylon 6, which is 165×1 and odyne/modulus, but it is much lower than that of commercially available high-tensile fibers (2.7 to 5.0×1 and odyne/ e/
It can be said that this value is significantly higher than that of In addition, the Young's modulus of zone heat-treated polypropylene fiber is 21.7×
The crystalline elastic modulus of polypropylene is 34×1 odyne/mm, which corresponds to approximately 2/3 of that of polypropylene. In addition, regarding other mechanical properties of the fiber obtained by the present invention, such as dynamic magnetic modulus and breaking strength,
As shown in the examples below, this value is considerably higher than that of those heat-treated by other methods.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, each measurement item in the example was based on the method described below. tl} Measurement of Young's modulus, breaking strength, and breaking elongation.
01 Type (Toyo-Baldwin).

The initial length of the sample was boiled for 2 minutes at room temperature, and the stress-strain curve was determined under the conditions of approximately 65% RH. From this, the Young's modulus, breaking strength, and breaking elongation were calculated using the conventional method (Japanese Industrial Standards, tensile strength of fibers). It was determined by the test method VISLI069). ■ Measurement of dynamic viscoelasticity The measurement temperature range for polyethylene terephthalate is from room temperature to around 200 oo, and for nylon 6 from room temperature to around 170 oo.
It was up to qo.

The sample used was a single fiber with an initial length of 2mm. The device is VmRON
By Low Type (Toyo-Mother ldMn).
In addition, driving frequency 110Hz, temperature increase rate 3.6℃/mi
n (PET) and 1.5q○/min (nylon 6)
And so. {31 Measurement of back refraction Using a polarizing microscope equipped with a Bereck compensator, in air, 20 to 250
Measurements were made using white light as the light source under conditions of 0.0 and RH of approximately 65%.

In addition, in the case of a sample having high retardation such as polyethylene terephthalate, an X-Z plate cut from a quartz single crystal was used as a compensating plate. {4) Measurement of density and calculation of degree of crystallinity Density was measured at 25.0 oo by the float-sink method using a toluene-carbon tetrachloride mixed solvent.

The degree of crystallinity is defined as the measured density, for example, by
2, 51 (1966). In addition, in the case of polyethylene terephthalate, the crystal density is 1.45, the amorphous density is 1.335 mm/ground, and nylon 6
In the case of , it was set as 1.230 and 1.083 nights/clump, respectively. Example 1 In this example, more preferable conditions will be investigated regarding the temperature of the heating furnace, the moving speed of the heating furnace, the tension applied to the sample, and the number of heat treatments when the apparatus shown in FIG. 1 is used.

As-spun polyethylene terephthalate fibers having a diameter of approximately 0.5 were used as the fibrils.

The birefringence of this fiber was 0.3 x 10-3, and the crystallinity determined by the density method was 1.8%. The conditions for zone stretching are that the stretching temperature is set to Tg of polyethylene terephthalate.
(69:00) and lower than the low-temperature crystallization temperature (12 p○), and the tension was set as low as 0.3 k9/fence. The heating furnace was moved at a speed of 4 min/min, and the fibers were moved from the bottom to the top. At this time, the fibril was easily drawn with some necking. The stretching ratio was 2.5 to 3.9 tones. The thus zone drawn fibers were then subsequently zone heat treated in the same equipment. As the heat treatment conditions, the temperature of the heating furnace was set to 210°C, the moving speed was set to 10 sides/min, and the number of heat treatments was set to 5 times, and the tension applied to the fiber was variously changed to determine the Young's modulus of the obtained fiber and the tension applied to the fiber. The correlation with tension was investigated. The result is the second
As shown in the figure. As is clear from Figure 2, the tension during zone heat treatment shows a maximum of Young's modulus around 16 kg/ground.
If the tension is greater than that, the Young's modulus is decreasing. This is thought to be because as the tension becomes excessive, distortion and local breakage occur in the fibers. A similar relationship is obtained between heat treatment and Young's modulus, with excessively high temperatures causing whitening and cutting of the fibers. Similarly, numerous tests were conducted to find more favorable conditions regarding the relationship between heat treatment temperature and Young's modulus. As a result, the conditions shown in Table 1 were determined as suitable conditions. The number of heat treatments gradually becomes constant when the number of heat treatments is 3 or more times, but it was considered that about 5 times is more preferable. Table 1 Example 2 This example shows the results of measuring the mechanical properties, orientation, and crystallinity of the raw fiber, zone-stretched fiber, and zone heat-treated fiber of Example 1.

From these measurement results, it is possible to know the progress of each stage of higher-order tissue formation. Table 2 shows the measurement results of Young's modulus, breaking strength, breaking elongation, birefringence, and crystallinity.

Table 2 The numbers in parentheses indicate the results of the second measurement.

As is clear from Table 2, Young's modulus and breaking strength are small when zone-stretched, but are significantly increased by zone heat treatment.

As for the microstructure, it can be seen from Table 2 that it exhibits fairly high orientation and low crystallinity at the stage of zone stretching, and that it changes into highly oriented, crystalline fiber when subjected to zone heat treatment. In particular, the value of birefringence, which indicates the degree of turning, is actually 0.
．． 247, which is higher than many previously reported values of crystal intrinsic birefringence. Further, FIG. 3 shows the temperature dependence of the dynamic elastic modulus E' and the loss elastic modulus E'' of the zone-drawn fiber and the zone-heat-treated fiber.

The white and black circles in Figure 3 are for the fibers after zone heat treatment, and the white and black triangles are for the zone-stretched fibers. be. As is clear from Fig. 3, the 8 value is significantly higher for the fibers after zone heat treatment over the entire temperature range, and in particular, the 8 value at room temperature is a high elastic modulus value of more than 20 , which is the highest elastic modulus value of commercially available polyethylene terephthalate strong yarn, 19.6 x 1
It is a value that exceeds the enemy. In addition, the Q dispersion peak observed in the temperature dependence curve of E'' is 90% for zone-stretched fibers.
℃, but in the fiber after zone heat treatment, it is found to be 130 qo, indicating that in the latter case, the thermal motion of the amorphous chains is significantly restricted. Example 3 In order to clarify what microstructure is responsible for the excellent mechanical properties of the fibers obtained according to the present invention, optical and x-ray measurements, infrared absorption spectra, DSC, creep, thermal Shrinkage and sardine viscoelasticity were measured.

From these measurement results, it is considered that the structure of the fiber obtained by the present invention is a tufted micelle structure consisting of almost perfectly oriented east-like crystals and fully extended amorphous chains.

FIG. 4 shows an X-ray Laue photograph of the zone-drawn fiber of Example 2 and the fiber after zone heat treatment. FIG. 4-a shows an X-ray Laue photograph of the zone-drawn fiber, and FIG. 4-b shows An X-ray Laue photograph of the fiber after zone heat treatment is shown.

As is clear from the comparison of these two drawings (photos), the zone-drawn fibers have low crystallinity to high orientation, while the zone-heat treated fibers have high crystallinity, but the zone-heat-treated fibers have high crystallinity. Moreover, it has high orientation.
FIG. 5 shows small-angle x-ray diffraction images of polyethylene terephthanate fibers stretched 5 times without tension and heat-treated and after zone heat treatment. Fig. 5-a shows a small-angle X-ray diffraction image of a 5-fold stretched untensioned heat-treated fiber, and Fig. 5-b shows a 4/corner x edge diffraction image of the fiber after zone heat treatment. These drawings (photos)
Therefore, in the former case, where the lamellae are sufficiently developed, the interference appearing on the meridian is strong and the long period is 118.6 A, whereas in the latter case, it is extremely weak and the long period is 15 A.
It is large at 4.2A. This decrease in periodic electron density fluctuations in the longitudinal direction suggests that the boundary between crystal and amorphous is unclear and that extended chain crystals are more dominant than lamellae. FIG. 6 shows the change in absorption based on the folding of the 988-arc molecular chain in the infrared absorption spectrum when zone stretching and further zone heat treatment are performed.

Figure 6-a shows the case of unstretched heat treatment without tension, and Figure 6-b.
The figure is a graph showing the infrared absorption spectrum near the hold band (Fold bag nd) when the film is stretched 7 times, and FIG. In either case, for this measurement, a single-stroke film was prepared and then subjected to each treatment and subjected to measurement. As is clear from the change in absorption shown in Figure 6, the hold band that is observed in the unstretched, non-tension heat-treated film with sufficient lamella formation is not observed in the stretched film, but is very much observed in the stretched and tension-heat-treated film. It can be seen that this is recognized as a weak shoulder-like peak. Although the film after zone heat treatment was not measured,
Regarding the films heat-treated at the same temperature and under the same tension, it can be said from this result that a small amount of hold chain crystals (Foldchain crystal 1) is present. This is due to overgrowth (O
ver-mother oMh). Next, DSC
Measurements were made on the curve.

Polymer, 14,4630973]
, Polymer (PolMmer), 18,647 [197
7] and the Polymer Science Society of Japan “Molecular Design of Polymers” Baifukan [
1971], p. 135, there are two types of melting peaks that appear in DSC curves: the high-temperature melting peak is based on the extended chain crystal, and the low-temperature peak is based on the melting of the folded Kinnada crystal. Are known. In the case of polyethylene terephthalate/terephthalate, two peaks appear at 248° C. and 258 qo in the DSC curve of the sample containing both types of crystals, and the melting peak of the fiber after zone heat treatment was close to the latter temperature castle. That is, it is considered to be based on the melting of extended chain crystals. Next, we measured the creep and thermal shrinkage of the sample, which provides insight into the state of aggregation of molecular chains in the amorphous region.

The measurement results showed that no cleavage occurred up to 200 qo, and the heat shrinkage was only about 4%, and compared to the case of ordinary yarn, the fibers after zone heat treatment had extremely excellent dimensional stability. Proven. This suggests east-like aggregation in which the molecular chains in the amorphous region are fully extended and densely packed. The low mobility of the amorphous chains can also be inferred from the fact that the Q dispersion obtained by mechanical viscoelasticity measurements is broad and occurs at high temperatures. From the above results, it is assumed that the fiber after zone heat treatment has a tufted micellar structure consisting of almost perfectly oriented east-shaped crystals and fully extended amorphous chains.

If such a structure is adopted, the approximately 40% amorphous region is considered to greatly contribute to stress retention and to the elastic modulus and strength. Example 4 In this example, the microstructure and mechanical properties are compared with fibers obtained by other heat treatment methods.

As other heat treatment methods, heat treatment under tension, heat treatment under tension, and heat treatment under no tension were performed. Heat treatment under tension is
After stretching the fibril 5 times at 90qo, the temperature is 200qo,
It was heat-treated in an air bath for 30 minutes at a tension of 16 kg/me. Heat treatment under constant length and heat treatment without tension are similar to heat treatment under tension, in which the bride fibers are stretched 5 times with 9030 and then heat treated in an air bath for 30 minutes under constant length and without tension, respectively. Note that the manufacturing conditions for the fibers after the zone heat treatment were the same as in Example 1. The mechanical properties, orientation and crystallinity results of the fibers obtained with these three different heat treatment methods are shown in Table 3 in comparison with the zone heat treated fibers of the present invention.

Table 3 The numbers in parentheses indicate the results of the second measurement.

From Table 3, it can be seen that Young's modulus and breaking strength are the highest for the fibers after zone heat treatment, and then decrease in the order of tension, constant length, and non-tension heat treatment.

From this, it was found that the greater the tension applied to the sample, the better the mechanical properties, and that local heating has a greater effect on heat treatment than uniformly heating the entire sample under the same tension. The fibers after zone heat treatment also have the highest birefringence, and it is thought that the orientation, especially the orientation of the amorphous chains, directly contributes to improving the mechanical properties. FIG. 7 is a graph showing the temperature dependence of the dynamic elastic modulus field.

Open circles indicate fibers after zone heat treatment, black circles indicate fibers after heat treatment under tension, open triangles indicate fibers after heat treatment under constant length, and black triangles indicate fibers after heat treatment under no tension. . It can be seen that among these four types of heat-treated products, the dynamic elastic modulus E' of the fiber after zone heat treatment exhibits the highest value over the entire temperature range. FIG. 8 is a graph showing the temperature dependence of tan6 of the four types of heat-treated products.

It is clear that the intensity of the n6 peak decreases as the heat treatment is performed under no tension, under constant length, under tension, and under zone heat treatment, and the intensity of the n6 peak decreases, becoming a flow, and the peak gradually shifts to the higher temperature side. Table 4 shows a comparison of the tan6 peak temperatures of fibers under tension, constant length, no tension, and zone heat treatment.

Table 4 Comparison of peak temperatures in Table 4 shows that the temperature increases in order from 120 oo for fibers heat-treated under no tension, and reaches 14,000 oo for fibers after zone heat treatment.

Since this dispersion peak is considered to be Q dispersion based on micro-Brownian motion of the amorphous chain segment, comparison of the temperatures of this dispersion peak provides an indication of the degree of thermal mobility of the amorphous chain. From this, it is clear that even after the zone heat treatment, the fibers are in a constrained state in which the mobility of the amorphous chains is low. Example 5 In this example, nylon 6 fibers having an as-spun birefringence of 0.5 x 10-3 and crystallinity of 27.7%, approximately 0.5 stiff diameter, were used as the fibrils. Similarly, we investigated more favorable conditions such as the temperature of the heating furnace, its moving speed, the tension applied to the sample, and the number of heat treatments.

The results are shown in Table 6. Table 6 In this study, even when nylon 6 fibers were used as the fibrils, the behavior was similar to that in Example 1, in which polyethylene terephthalate fibers were used as the fibres.

Example 6 This example shows the results of measuring the mechanical properties, orientation, and crystallinity of the fibrils, zone-stretched fibers, and zone-heat-treated fibers shown in Example 5.

Table 7 shows Young's modulus, breaking strength, breaking elongation, back refraction, and crystallinity. Table 7 As is clear from Table 7, in the case of nylon 6, as in the case of polyethylene terephthalate shown in Example 2,
It can be seen that it exhibits excellent mechanical properties, orientation, and crystallinity.

Regarding Young's modulus, the fiber after zone heat treatment is 8.3×
It shows the value of commercially available high tensile strength fiber (2.
7 to 5.0×1biod skin e/flow), this shows a considerably higher value. Table 7 also shows that although the fibers after zone heat treatment have a very high degree of crystalline and amorphous chain orientation, they exhibit a crystallinity of 48.9%, and the nylon 6 fibers are continuous over a fairly wide range. It is thought to consist of a highly oriented tufted micellar structure with a crystalline phase. Example 7 In this example, as in Example 4, the microstructure and mechanical properties are compared with fibers obtained by other heat treatment methods.

The conditions of heat treatment under tension, heat treatment under constant length, and heat treatment under no tension mentioned here are all suitable in that the fibril is stretched 3 times at room temperature and then heat treated, but heat treatment under tension is In contrast, heat treatment is performed at 175qC for 30 minutes under a tension of 10k9/base, while heat treatment is performed at 200°C under a constant length.
, heat treatment under no tension for 30 minutes at 200°C under no tension, 3
In both cases, heat treatment was performed for 0 minutes in a vacuum chamber. The mechanical properties, orientation and late crystallinity results of the fibers obtained by these different heat treatments are shown in Table 8 in comparison with the zone heat treated fibers of the present invention.

Table 8 As is clear from Table 8, the case of nylon 6 not only shows the same tendency as the case of polyethylene terephthalate shown in Example 4, but also the case of nylon 6 with other heat treatment methods. It can be seen that the mechanical properties are extremely superior compared to the fibers obtained by the method.

FIG. 9 shows the temperature dependence of tan6 of the above-mentioned four types of heat-treated products, and this case also shows the same orientation as in the case of polyethylene terephthalate fiber.

Table 9 shows a comparison of n6 peak temperatures under tension, constant length, no tension, and zone heat treatment.

Table 9 Example 8 In this example, an example of application to crystallized polymers other than the above-mentioned polyethylene terephthalate and nylon 6 is shown for confirmation.

This figure shows the Young's modulus of IT-polypropylene and polyethylene fibers produced according to the method of the present invention, including those of the polymer fibers described above. As is clear from Table 10, Item 1, it was further confirmed that the method of the present invention could be applied to other crystalline polymers such as IT-polypropylene and polyethylene.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an apparatus used in the present invention. In Figure 1, 1 is a crosshead, 2 is a heating furnace or band heater, 3 is a sample, 4 is a holder, 5 is a chuck, and 6
indicates a rod-shaped object, and 7 indicates a guide. Fig. 2 is a graph showing the relationship between tension and Young's modulus, and Fig. 3 is a graph showing the relationship between temperature and dynamic elastic modulus E', and temperature and loss elasticity E''. Figure a is an X-ray Laue photograph of the zone-stretched fiber, Figure 4-b is an X-ray Laue photograph of the fiber after zone heat treatment, and Figure 5-a is an X-ray Laue photograph of the fiber after zone stretching. Figure 5-b is a small-angle X-ray diffraction photograph of the bottom heat-treated fiber, and Figure 5-b is a small-angle X-ray diffraction photograph of the weave length after zone heat treatment. Figure 6-a, Figure 6-b, and Figure 6-c. The figure is a graph showing infrared absorption spectra when unstretched and heat treated under no tension, when stretched to 7 times, and when heat treated under tension after 7 times stretching. Fig. 8 and Fig. 9 are graphs showing the dependence of tan8 temperature on heat-treated products. Fig. 1 Fig. 2 Fig. 3 Kojimori Utasame; Kotosan Sankoji Kama-o scale-vine-fune koji spell - Guniso Fig. 6-o Fig. 6-b Fig. 6-c Fig. 7. Fig. 8 Fig. 9

Claims (1)

[Claims] 1. In zone stretching, an amorphous or as low-crystalline thermoplastic synthetic fiber as possible is stretched under tension through a short heating zone at a temperature from its glass transition point to its crystallization temperature while being locally heated from the surroundings. Amorphous or low-crystallinity highly oriented fibers are produced, and zone heat treatment is performed in which the resulting fibers are passed through a short heating zone at a temperature above the crystallization temperature while applying a high degree of tension to fully extend the molecular chains. A method for producing high-modulus, high-strength fibers characterized by local heat treatment from the surrounding area.