JPS61167015A - High-modulus fiber and its production - Google Patents

Abstract

PURPOSE:A solution of poly(p-phenylene terephthalamide) in concentrated sulfuric acid is extruded through the spinneret into the coagulation bath and the coagulated fibers are accumulated on the net conveyor, adjusted in their water content and dried to give the titled fiber which is suitable for reinforcing resins, because the fibers have high impact strength. CONSTITUTION:A poly(p-phenylene terephthalamide) with inherent viscosity of higher than 5.0dl/g is dissolved in concentrated sulfuric acid of 97-101wt% to form a spinning dope of 17-20wt% polymer concentration. The resultant dope is extruded into a gas atmosphere, then into a coagulation bath 1a at -10-25 deg.C. The formed yarn 3b is accumulated on a net conveyor 6 and washed with the washer 8 so that the water content of the yarn is adjusted to 20-80wt% on the net conveyor 6. Then, the yarn is dried under tension of 5-15g/denier at 50-180 deg.C in the dryer 10 until the water content reaches down 0.1-1.5wt% to give fibers having fine crystal size of 35-55Angstrom , density of more than 1.43g/cm<3>, crystal orientation angle of less than 14 deg., filament elongation of less than 3.3%, filament modulus of less than 750g/d, filament strength of less than 25g/d and temperature factor of temperature more than 1.05.

Description

DETAILED DESCRIPTION OF THE INVENTION ■ Industrial Field of Application The present invention relates to a high modulus type poly(p-)22-terephthalamide P) (hereinafter sometimes abbreviated as PPTA) fiber and its manufacturing method. More specifically, the present invention relates to a high modulus PPTA fiber with excellent impact strength and a method for producing the same, and this fiber is suitable for reinforcing glass, clay, etc.

■ Conventional technology It is known that high-strength, high-monocular fibers can be obtained from PPTA (for example, Japanese Patent Laid-Open No. 47-39458,
(Japanese Unexamined Patent Publication No. 47-43419). Among these, JP-A No. 47-39458 basically discloses a medium modulus type fiber, which is a fiber used in a field different from the high modulus type fiber, which is the subject of the present invention. . On the other hand, Japanese Patent Application Laid-open No. 47-43419 discloses that PPT
It is disclosed that a high modulus type PPTA fiber can be obtained by air discharge wet spinning using a high concentration dope of A and then subjecting it to tension heat treatment. Kepler 49 is used as a fiber produced by this method. However, it has been found that high modulus type PPTA fibers produced by such tension heat treatment have low impact strength.

Since then, many methods for producing high modulus type PPTA fibers have been disclosed (for example, JP-A No. 49-110
913, JP-A-52-12325, JP-A-52-12326, JP-A-55-1324, and JP-A-F+5-122011), most of which involve stretching. However, according to the knowledge obtained by the present inventors, the above-mentioned drawback of low impact strength has not been improved at all. In addition, it also has the disadvantage that thermal deterioration and increase in fluff are inevitable.

On the other hand, several methods have been proposed for producing high modulus type PPTA fibers without tension heat treatment. For example, JP-A-53-98415 discloses a method of drawing wet fibers in an inert gas at a temperature of 200° C. or less. However, in this method, the starting fibers remain with a sulfuric acid content of 130 to 14
It contains 0% water and is prone to thermal deterioration, so it is necessary to use expensive inert gas, and the strength of the obtained fiber is low, making it impossible to achieve the goal of having both high strength and high modulus. In addition, the fibers shown in the examples have defects such as being relatively weak against impact, probably because unnecessary tension is applied during the washing process and the initial drying process. Further, JP-A No. 59-47421 describes that a high modulus fiber can be obtained by applying tension in a specific coagulation state. However, the fibers obtained by this method have insufficient impact strength. Furthermore, in JP-A-47-39458, in addition to the description in the last part of Example 1, which shows the hot drawing method for reference, fibers that have a relatively large modulus as spun are exemplified. (For example, Example L3.@, 6). However, since some of them have low strength, and all of them are washed with water under tension, their impact strength is relatively low.

■ Problems to be Solved by the Invention The present invention aims to solve the above-mentioned problems of the prior art.Specifically, high modulus fiber useful for reinforcing plastics, This is an epoch-making product that attempts to achieve both high strength and high impact strength. And, such highly desirable fibers have certain novel structural properties and are produced by air-gap spinning a highly concentrated dope of PPTA with a high degree of polymerization and by a new and specific manufacturing method. They discovered that this could only be achieved by a method of coagulating under tension, washing with water, and drying to a specific moisture content, and then drying under high tension and at a relatively low temperature until a specific moisture content was achieved. The present invention was completed based on this discovery.

5. Means for solving the problem, that is, the first aspect of the present invention is to have a 1g crystal; A fiber consisting essentially of poly(p-7 enylene terephthalamide) with a logarithmic viscosity of O61717 or higher, and a high modulus fiber that satisfies all of the following (A) to (G): (A) Apparent microcrystals Size = 35-55 Å (B) Density ≧1.43 fi/α5 ((F) Crystal orientation angle 514 degrees Q) Single fiber elongation ≦3.3 chi ([::) Single fiber m modulus ≧750 g77″ Neil (F) single fiber strength≧25g/denier (G)Temperature coefficient of strength≧1.05, and the second aspect of the present invention is poly(p-phenylene terephthalamide) with a logarithmic viscosity of 5.0 dt or more than 79. A dope obtained by dissolving 97 to 101% by weight of concentrated sulfuric acid to a polymer concentration of 17 to 20% by weight was placed in a spinneret and placed in a gas of -10°C.
After extruding and coagulating the yarn into a coagulation solution at 25°C, the yarn is deposited on a net conveyor and washed, and then the moisture content of the yarn is adjusted to 20 to 80% by weight on the net conveyor. 50 to 50 to 50 to 100 ml until the moisture content reaches 0.1 to 1.5 weight by applying a tension of 5 to 15 g/denier (denier is based on the fiber after drying) to the strip.
A method for producing a high modulus fiber characterized by drying at 1so°C.

The polymer used in the present invention consists essentially of PPTA. Here, the meaning of "substantially" means that the amount of I remer other than PPTA [e.g.
Poly-(m-7 enylene terephthalamide), Poly-(
p-phenylene inphthalamide), poly-(m-phenyleneiso7thalamide), poly-(I rimethylene terephthalamide), aliphatic polyamide, alicyclic polyamide 1, / IJ ester, polyimide, polyurethane, I
PPTA is blended with other repeating units (e.g., nuclear-substituted p-phenylene units, nuclear-substituted or unsubstituted biphenylene units, p-phenylene units, m-phenylene units, etc.). (Poly)methylene units, pyridylene units, bonding units such as esters, urethanes, ureas, ethers, thioethers, etc.) are copolymerized, and various additives and compounding agents (such as dyes, antioxidants,
This means that UV absorbers, brighteners, pigments, etc.) may be added.

The poly(p-phenylene terephthalamide) constituting the fiber of the present invention is at least 5.0 dl/Ii or more, more preferably 5.5 dl/Ii or more, and even more preferably 6.0 dl/Ii.
Logarithmic viscosity of 71 or higher (0.511/d in concentrated sulfuric acid at 25°C)
).

A high logarithmic viscosity means a high degree of polymerization, which is associated with high fiber strength.
There is 1. On the other hand, the high modulus fiber disclosed in the examples of JP-A-53-98415 has a small logarithmic viscosity of less than 4 dt711, and therefore has a small strength.

The fibers of the present invention should be composed of PPTA with a so-called summer crystalline form. Here, to explain a little about the crystal form of PPTA fibers, the PPTA fibers manufactured by the method of Kepler or Kepler 49, which is used as a top cloth, or, for example, in Japanese Patent Application Laid-open No. 47-39458, can be crystallized by X-ray diffraction. When we examine the structure, without exception, 2 on the equator line
Large diffraction peaks were observed at 0#23 degrees and 20#21 degrees ((a) in Figure 2), and Takayanagi et al. (Appl.

Polym, Sci, Volume 23, Page 915 (1
According to the definition of 979)], it can be said that it is a summer-type crystal. Takayanagi et al. proposed the ■ type as another crystal form of PPTA. Although it is stated that summer-shaped or ■-shaped crystals occur depending on the choice of coagulant in the production of PPTA film, there is no mention of fibers. Next, we will discuss how to determine summer type and ■ type. A wide sample of PPTA fibers is irradiated with X-rays from a direction perpendicular to the fiber length direction using a conventional method to obtain a diffraction pattern. Pay attention to the diffraction peak in the equatorial direction of the diffraction pattern (for example, record the diffraction intensity on the equatorial line in the range of 20#16 to 30°).

At this time, in addition to the large diffraction peak at 2θ #23°, 2
One with a diffraction peak at θ#210 ((a) in Figure 2)
is defined as a summer-type crystal, and one with a diffraction peak at 2θ #18° (← in Figure 2) is defined as a ■-type crystal. Note that when the summer type and ■ type are present together, both the 2θ #18° and 20 #210 diffraction peaks will be observed.

The relationship between the crystalline form of fibers and their properties has not been directly expanded or understood. However, L-type crystals are formed when the coagulation bath temperature is low, below -15°C, and when coagulating at such temperatures, the viscosity of the coagulation bath increases, causing a large tension to be applied to the coagulation thread. This is undesirable because the strength cannot be increased, the impact strength is insufficient, and fuzz and so-called single thread breakage are more likely to occur.

In the present invention, PP having all or most of the summer-type crystal form
The subject is TA fiber.

The fiber of the present invention has an X-ray diffraction peak of 35 to 55, as measured by the method described in JP-A-55-122012, with respect to the X-ray diffraction peak appearing between 20 and 22 degrees.
It has an apparent microcrystal size of X. This requirement is closely related to the fact that the fibers of the present invention are very high modulus fibers and therefore have improved impact resistance. Furthermore, it is associated with other characteristics such as being less likely to fibrillate and having greater nodule strength. The apparent size of the microcrystals is preferably 40 to 55X, more preferably 4
It is 5-52X. In this way, in order to obtain a high modulus of PPTA fibers, it is necessary that the molecular chain orientation required for high modulus be achieved at low temperatures, since the crystallite size is relatively small. . That is, the fibers of the present invention can be dried at 180° C. or lower under high tension from a moisture content of 20 to 80% by weight to a moisture content of 0.1 to 1.5% by weight, thereby reducing molecular weight. Most of the conventional techniques disclosing high modulus PPTA@fibers, for example, JP-A No. 47-43419, are obtained by increasing the chain orientation, and this structural parameter of the apparent crystallite size Publication, JP-A-49-110
913, JP-A-52-12325, JP-A-52-12326, JP-A-55-1324, JP-A-52-122011, etc. by drying tension heat treatment accompanied by stretching. It can be distinguished from fibers obtained by a method in which the process is carried out at a high temperature after finishing.

The fibers of the invention should have a density of at least 1.43 ji10n3. Density is 1.43 g/cyt'
If the fiber is smaller, it means that the fiber contains a lot of crystals, crystals, and gates, has extremely low crystallinity, and has a nonuniform aggregate structure, and has low strength. Practical value decreases. Such low density fibers may be obtained, for example, by wet spinning directly from a spinneret into a coagulation bath, or by spinning with very low draft or polymer concentration. The density of the PPTA of the present invention can be measured in a conventional manner using toluene and carbon tetrachloride at 25° C. using a density gradient tube.

The PPTA fibers obtained by the method disclosed in Japanese Patent Publication No. 47-2489 and Japanese Patent Publication No. 50-8474 have a density of less than 1.41 i/an' due to a disordered agglomerated structure, low strength, and nodules. The strength of the fiber of the present invention is extremely low.
It should have a crystal orientation angle of 14° or less, as measured for the X-ray diffraction peak at 2θ #23° according to the method described in JP-A-55-122012. This is because it is difficult to guarantee a high modulus for PPTA fibers that do not meet this requirement. The crystal orientation angle is preferably 13° or less, more preferably 11° or less. Fibers having a crystal orientation angle of 14° or less can be obtained by so-called gear lag spinning followed by high tension treatment in the subsequent stage of drying.

The fibers of the present invention also have a single fiber constancy of 3.3% or less. Single fiber elongation is determined from Japanese Patent Application Laid-Open No. 1983 (1973) for single fibers
Measured according to the measurement method disclosed in Japanese Patent No. 39458. However, in the method described in the same publication, the length of the measurement part is 1
Due to the short length of 1 inch, slippage at the gripping part of the sample is often seen as a source of error. For this reason, for example,
It is desirable to confirm the true elongation using the method described in ASTM 01906-62T. Due to the above-mentioned limitations regarding the monofilament fibers, the fiber of the present invention is disclosed in Japanese Patent Publication No. 47-394
It can be clearly distinguished from the fiber of Publication No. 58.

Furthermore, since the fibers of the present invention have a fiber moss of 750g/50y/denier, the fibers of the present invention require particularly excellent deformation resistance when used as reinforcing fibers for glasstics, rubber, etc. When used as reinforcing fibers in composite materials, it creates tremendous value. The single fiber modulus of the present invention is measured by changing the gripping length of the sample to 20 cJn in the method described in JP-A-47-39458. This is because, if the method described in the above-mentioned publication is used as is, the influence of the sample slipping in the gripping portion is large, as described above. The fibers of the present invention preferably have a single fiber modulus of 80 (1/denier) or greater.

The fiber of the present invention has a strength of 25y when measured as a single fiber.
/ more than one denier. Measurement of strength is based on JP-A-47-39
This can be done by the method disclosed in Japanese Patent No. 458. The higher the strength, the more useful it is for use as a reinforcing material, and from this point of view, a single fiber strength of 28 i/y” neel or higher is useful, and 30 g/y
Denier and above are most useful. The reason why the fiber of the present invention has high modulus and high strength is that the fiber has a high degree of polymerization.
In addition to being made of PTA, during the spinning process, the application of tension to highly orient the molecular chains is kept to the minimum required in the late drying stage, and other processes such as coagulation, water washing, and pre-drying are done without tension or as much as possible. This is thought to be because the cracks, voids, etc. that cause a decrease in strength are extremely small because the strength is reduced. In this respect, the PPTA fibers disclosed in the examples of JP-A-53-98415 have a relatively low degree of polymerization, and also have a water content of 130 to 1.
The strength is somewhat low due to the fact that high tension is applied while drying from 40%.

The most important feature of the fiber of the present invention is that it has both high modulus and high strength, as well as excellent impact strength. The fiber of the present invention has an excellent temperature coefficient of strength as an index of impact strength.

The temperature coefficient of strength is the single fiber strength measured at -35℃ by 2
Measured at 0°C [Also refers to the number divided by the single fiber strength, for the fibers of the present invention it is 1.05 or more, preferably 1.10
That's all. Generally, the impact strength of a fiber is the strength when the fiber is subjected to rapid deformation, for example, rapid tensile deformation, so it can be said that the impact strength of the fiber is the strength when the fiber is subjected to sudden deformation, such as rapid tensile deformation. This is the strength when giving . Therefore, by placing the molecular chains in motion, lowering the temperature, and performing a tensile test, it is possible to easily measure properties that can be substituted for impact strength. The temperature coefficient of strength used in the present invention has such a physical meaning.

Within the knowledge of the present inventors, fibers having a single fiber strength of zs17 denier or more, a single fiber modulus of 750 g/denier or more, and a temperature coefficient of strength of 1.05 or more are known. isn't it. That's about 200
If the fiber is hot-stretched at a high temperature above ℃, if tension is applied at the initial stage of the washing or drying process, or if tension is applied during solidification, high modulus fibers can be created by increasing the orientation of the molecular chains. Although it is possible to create
This is because the strength often decreases and the temperature coefficient of strength is always less than 1.05. That is, in the fibers of the present invention, high tension is applied to the fibers at a low temperature concentrated in the late stage of drying when the molecular chains can be most effectively oriented without causing relaxation, while at the same time promoting molecular chain orientation. In other processes, which are less effective, this can only be achieved by using a special manufacturing method in which no tension is applied at all or only the minimum possible tension is applied to the fibers.

Although the thickness of the fiber of the present invention is not particularly limited,
Usually, monofilaments of 0.1 to 5 deniers are useful. The number of filaments is not particularly limited, and can range from monofilament to 10,000 or more yarns or cords,
It may be used as woven fabric, nut fP strand, fibrid, etc. Although the cross-sectional shape of the single fiber is not particularly limited, it is usually a circle or a shape close to a circle.

The fibers of the present invention have an extremely large modulus and are useful as reinforcing fibers for materials such as glass, wood, and rubber, and particularly for reinforcing materials that require high deformation resistance. In such applications, known high modulus fibers, such as JP-A-47-43
Since it has superior impact resistance compared to the fibers disclosed in Japanese Patent No. 419 and the Kepler 49 used as a top cloth, it is particularly useful as a reinforcing fiber for composite materials that require such performance. The fibers of the present invention also have the characteristics of being difficult to fibrillate and can be manufactured at low cost, and have great industrial advantages in terms of both the composite material manufacturing process and the product performance of the composite material.

The fiber of the present invention can only be produced under specially specified operations and conditions, and this production method constitutes the second aspect of the present invention.

In producing the fibers, first a dope is prepared by dissolving PPTA with a logarithmic viscosity of 5.0 dt/g or more in 97-101% by weight concentrated sulfuric acid to a polymer concentration of 17-20% by weight. . At this time, as described above, PPTA may be copolymerized with other components if necessary, or may be blended with other polymers in small amounts. Furthermore, since PPTA generally causes a slight decrease in the degree of polymerization in a doped state, the degree of polymerization of the charged PPTA may be determined in consideration of this point. In order to ensure desired levels of physical properties in the fibers of the present invention, it is preferable to use PPTA with a logarithmic viscosity of about 5.2 d4/,p or more.

As a solvent for dope preparation used for spinning, 97 to 10
Concentrated sulfuric acid is used at a concentration of 1% by weight, preferably 98.5-100.5% by weight, most preferably 99.8-1001% by weight. Specifically, the concentration should be appropriately selected depending on the logarithmic viscosity of the polymer and the concentration of the polymer dissolved in Dogue used for spinning. When the concentrated sulfuric acid concentration is less than 97% by weight, the solubility of the polymer is poor, and therefore a suitable dope for spinning cannot be obtained, and the viscosity of the dope increases, making it difficult to transport and filter. The mechanical properties of the resulting fibers are unsatisfactory. On the other hand, if the concentration of concentrated sulfuric acid exceeds 101% by weight, ie, fuming sulfuric acid containing a large excess of 803, it is difficult to handle, and moreover, the polymer hardly dissolves. Small excess S
It is known that in fuming sulfuric acid containing O, at a concentration of 10<1>- or less, the solubility of Tellimer is good and a preferable spinning doug can be obtained. However, the presence of a large excess of SO in concentrated sulfuric acid creates voids in the internal structure of the resulting fibers, resulting in low fiber density, dull appearance, and poor mechanical properties. , and the maximum possible withdrawal speed from the coagulation bath also decreases.

The dope used for spinning is 173i to make it highly monolithic.
It is necessary to prepare it so that it contains poly(p-7 enylene terephthalamide) in an amount of % or more.

In addition, a high degree of polymerization with a logarithmic viscosity of 5.0617 g
In the case of PPTA, it is difficult to dissolve more than 20% by weight in concentrated sulfuric acid. From the point of view of producing high-strength, high-modulus fibers, the 4+J concentration is 19
It is more preferable that the amount is 20% by weight.

The temperature of the spinning dough is preferably any temperature between about 100° C. and the lowest temperature at which the spinning dough exhibits optical anisotropy and has sufficient fluidity to be handled. Specifically, the temperature of the spinning doug is appropriately determined in consideration of the polymer concentration, sulfuric acid concentration, spinneret orifice diameter, discharge linear velocity, and the like.

The dough thus prepared is extruded through a spinneret into a gas and then into a coagulation bath. It may be preferable, especially for industrial production, to degas, filter and weigh the doug before passing through the spinneret. The shape of the spinneret, the number of holes, the size of the holes, etc. are not particularly limited. The diameter of the hole is usually 0.01 to 0.5 m. The linear speed of the dough extruded from the spinneret is not particularly limited, and may be determined solely based on requirements such as productivity and draft. It is important that the dope stream extruded from the spinneret is first passed through a gas. This is because when extruding from a spinneret into a continuous coagulation bath without passing gas, it is difficult to increase the draft to more than 1.5, and the resulting fibers have a low density.
This is because the strength is also small. Gases include air, nitrogen,
Examples include argon and oxygen. economic benefits,
Air is most preferable from the viewpoint of operability. The gas thickness, i.e. the distance between the spinneret and the coagulation surface, is approximately 0.2 to 50 cm (
Leprosy is appropriate. The dope stream forced into the gas must then be forced into a coagulation bath where it undergoes coagulation.

The coagulating liquid should be maintained within a temperature range of -10°C to 25°C. If the temperature of the coagulating liquid exceeds 25° C., the density of the fibers becomes low and the strength becomes less than 259/denier, which is not preferable. Additionally, when the temperature of the coagulating liquid drops to more than 110°C, the viscosity of the coagulating liquid generally increases, making it unavoidable that high tension is applied to the coagulated yarn during spinning, as well as decreasing the coagulating rate and coagulating. Since such tension is applied to yarns with a low progress rate, the strength of the fibers may be reduced, and the impact resistance of the fibers may also be reduced, which is not preferable. Furthermore, when solidified at a temperature lower than -10°C, PPTA fibers with a ■-type crystal form are produced, whereas at temperatures above -10°C, all or most of the fibers become a ■-type crystal form. The fiber of the present invention is obtained. The temperature of the coagulating liquid is preferably -10°C to 15°C.

Water is preferably used as the coagulating liquid, but monohydric or polyhydric alcohols such as methyl alcohol, ethylene glycol, glycerin, and ingropanol, mixtures of water and the above-mentioned alcohols, or aqueous solutions of acids such as sulfuric acid,
Aqueous alkaline solutions such as ammonium hydroxide and calcium chloride 7
Aqueous solutions of various salts such as um are used.

The shape of the coagulation bath is not particularly limited. However, from the viewpoint of avoiding unnecessary tension being applied to the yarn during coagulation, it is recommended to use a so-called funnel-shaped coagulation bath in which 1 m of coagulation liquid falls together with the running yarn, as shown in 1b of Figure 1. Preferably, such a coagulation bath is also preferred in terms of maintaining the spinning speed at a high level in industrial production. Also,
It is preferable to make the coagulation liquid depth (t) in FIG. 1 as small as possible, since this reduces the tension on the coagulated filament.

Generally, the lower the tension on the coagulated thread, the more
The strength of the fibers increases and the impact strength also improves. The coagulation bath may have two or more stages if necessary.

The draft during spinning depends on the thickness of the gas layer, the diameter of the spinneret, the polymer concentration, the logarithmic viscosity of the polymer, etc.
It is usually selected in the range of 2 to 15, preferably 3 to 10. If the draft is too small, the orientation of the molecular chains tends to be insufficient, but the degree of draft can be compensated for by applying tension in the latter stage of drying. If the draft is too large, the stability of spinning may decrease and the strength of the fiber may also decrease.

Here, the draft is the value obtained by dividing the linear velocity of the coagulated yarn when it is drawn out from the coagulation bath by the linear velocity of the doag passing through the spinneret.

When taking out the coagulated thread from the coagulation bath, it is desirable to apply as little tension as possible. For example, it is better to use the deflection roller (9) in FIG. 1 as a rotary type with less resistance and to avoid using fixed pins or rods. On the other hand, in Japanese Patent Application Laid-open No. 59-47421, the molecular chain orientation is increased by applying a tension of 1 to 4117 deniers to the coagulated filament leaving the coagulation bath, and However, this method inevitably has the disadvantage that the impact resistance of the resulting fibers is reduced. In the present invention, it is preferable to apply only a tension of about 0.59/denier (denier is based on the fiber after washing and drying) or less to the yarn leaving the coagulation bath, and more preferably 0.59/denier or less.
Must be less than or equal to 3 g/denier, most preferably 0.211
It is 7 denier or less.

The coagulated threads drawn from the coagulation bath must be deposited on a net conveyor for cleaning. this is,
This is because applying tension to the yarn during the cleaning process is a major hindrance to ensuring excellent impact resistance. On the other hand, although JP-A No. 53-98415 states that it is generally possible to wash the coagulated yarn on a net conveyor, all of the examples show that it is possible to wash the coagulated yarn on a roller. The temperature coefficient of strength is smaller than that of the fibers of the present invention.

Washing is usually carried out in one or more stages with water, and may be combined with an alkaline aqueous solution such as caustic soda to perform this effectively. It is preferable to extract and remove sulfuric acid as much as possible by washing with water, and it is preferable to reduce the residual amount to about 500 ppm or less, preferably 100 ppm or less.

If necessary, the washed fibers are applied with an oil agent and dried, but in the method of the present invention, the water content is reduced to 20 to 80% by weight on a conveyor without any tension being applied following washing with water. need to be adjusted. The fibers washed with water according to the method of the present invention generally have a moisture content of 100 to 300% by weight as it is, so they can be dried to 20 to 80% by weight, preferably 3% by weight, by any method such as drying or suction.
The moisture content is between 0 and 70% by weight. For drying, hot air at room temperature to about 200°C, a hot plate, dielectric heating, infrared heater, etc. can be used.

In the present invention, the moisture content is reduced to 20% prior to high tension drying.
It is very important to adjust the content to ~80% by weight. This is because even if high tension is applied to fibers with a water content of more than 80% by weight, molecular chain orientation is not efficient; in other words, the orientation relaxation occurs considerably, leading to microscopic destruction of the fiber structure and decreasing impact strength. In addition, in industrial production, tension drying is a process in which there is a large loss of thermal energy due to the low degree of fiber accumulation. On the other hand, when fibers with a water content of less than 20% by weight are dried under high tension, the plasticizing effect of water molecules is small and the orientation of molecular chains due to tension does not proceed sufficiently, making it difficult to achieve high modulus. Note that the effects of the present invention cannot be achieved by a method in which the fibers are once dried and then rewetted.

The fibers, whose moisture content has been adjusted to 20 to 80% by weight on the net conveyor, are unwound and processed to have a moisture content of 5 to 15% by weight. It is dried under the tension of @/7″ kneader at a temperature of 50 to 180° C. to a moisture content of 0.1 to 1.5% by weight.

The tension during drying is preferably from 5 to 12 g/denier, where the denier is based on the fiber after drying. When a tension of 5 to 15 g/denier is applied, the fibers are stretched by about 2 to 8%.

High modulus is not achieved at tensions below 5 g/y'neal. On the other hand, if a tension exceeding 15 g/denier is applied, the strength will drop significantly and the fibers may even break.

The temperature for high tension drying is selected from the range of 1-150 to 180°C. Below 50°C, drying efficiency is poor and productivity is poor. At temperatures exceeding 180°C, it is difficult to control the drying end point, and the apparent size of microcrystals may decrease by 5° due to excessive crystal growth.
It is possible to exceed 5X. The drying humidity is preferably 100 to 150°C.

The high tension drying time is such that the moisture content of the fiber at the end of drying is 0.
The amount may be determined to be 4 to 1.5% by weight, taking into consideration the denier of the fiber, the number of filaments, the capacity of the heat source, the heat transfer efficiency, etc. The moisture content at the end of drying is critical to the performance of the fiber. If tension application is stopped when the water content exceeds 1.5% by weight, relaxation of the molecular chain orientation tends to occur, and the modulus may reach an insufficient level. Applying tension to a moisture content of less than 1% by weight is not only undesirable in terms of energy loss, but also increases the occurrence of fuzz and the apparent size of microcrystals exceeding 55X, which is a serious problem. The characteristics of the inventive fibers are lost.The moisture content after high tension drying is preferably between 0.3 and 1.2% by weight.

The method and apparatus for drying under high tension are not particularly limited, and examples include a method of applying tension with a heated roller as shown in Figure 1, a method of running under tension in an atmosphere of 50 to 180°C, a method of dielectric heating. Industrial methods include a method in which the vehicle is run while applying tension, a method in which the vehicle is run while being in contact with a hot plate while applying tension, or a method in which these methods are used in combination.

Figure 1 shows an embodiment in which high-tension drying is carried out directly and continuously after moisture adjustment. Although this method is preferred because it can be carried out industrially and efficiently, it is not limited to this method. After the adjustment, the fibers may be rolled up and dried again batchwise or semi-continuously under high tension.

The atmosphere during drying is usually air from the point of view of cost and convenience, but depending on the purpose, it may be carried out in an inert gas such as nitrogen or argon.

■ Effects of the Invention The method of the present invention involves applying high tension to PPTA fibers in a specific moisture content range in which molecular chain orientation occurs most efficiently and does not cause orientation relaxation, thereby causing a high degree of molecular chain orientation. The fiber of the present invention is a novel PPTA fiber with unique properties obtained through this process, which is based on a new and unprecedented technical idea of never applying unnecessary tension in the process of leaving the fibers. .

Therefore, the characteristics of the present invention are, firstly, that the fiber has both high strength and high modulus, and also has high impact strength, which is different from the conventionally known high modulus type PPTA. IJt! This is a big difference between the two.

In addition, when evaluated from an industrial manufacturing perspective, it has the following characteristics: it generates little fuzz, the process is stable, it can be manufactured directly from spinning, and it can be manufactured at low cost because there is little energy loss.

Utilizing these characteristics, the fibers of the present invention are useful as reinforcing materials for rubber such as various belts, and reinforcing materials for plastics, and are particularly used by taking advantage of their high impact strength. When fibers are used to reinforce these rubbers and plastics, they are usually used in the form of multifilaments, but the fibers of the present invention are not limited to this.
In the form of monofilament, roving yarn, fabric, chopped strand, etc., it can also be used as rope, woven fabric, reinforcing material for plastics, metal, cement, ceramics, etc., cotton, etc. ◎Example 1 and comparison Example 1 PPTA having a logarithmic viscosity of 5.8 was obtained according to the reference example of JP-A-55-122011. Using this PPTA, PPTA fibers were produced using the apparatus shown in FIG.

PPTA in 99.8% sulfuric acid with a polymer concentration of 19% by weight
The mixture was dissolved at 75° C. and defoamed under reduced pressure for about 2 hours. While filtering the dope exhibiting optical anisotropy maintained at 75 to 80°C, it was extruded through a spinneret (2 in Figure 1) having 100 pores with a diameter of 0.065+m, and passed through air at a distance of about 5 m. After running, it was extruded into a 30% by weight sulfuric acid aqueous solution (1&) maintained at -5°C. Draft 8, 30
The coagulated thread was removed from the coagulation bath at a speed of 0 m/min. The coagulated yarn was placed on a net conveyor (7) while being taken out so that only a tension of about 0.18 g/r (denier is based on dry fiber) was applied to the coagulated yarn. Wash the accumulated threads first with water, then with a dilute aqueous solution of caustic soda, and then again with water until the residual sulfuric acid is 80 ppm or less relative to the fibers, and then sprinkle with an oil agent (the oil agent application device is shown in Figure 1). After that (not shown), the moisture content of the deposited fibers (yarns) was adjusted using a moisture adjustment device (10 in FIG. 1). The moisture regulating device is approximately 2.5 m long and is divided into five blocks (10a to 10d) as shown in Figure 1, and each block independently controls water vapor at approximately 120°C. The structure was such that hot air heated by When all 5 blocks were operated at about 120°C (Comparative Example 1-i), when the other 4 blocks except 10& were operated at about 120°C (Example 1-1), and when all other blocks except 10a and job were operated at about 120°C, When the three blocks were operated at about 120°C (Example 1-2), when only 10d and low were operated at about 120°C (Example 1-2).
3), when only lOe was operated at about 120°C (Example 1
-4), the moisture content results for the case where all blocks were left at room temperature without heating (Comparative Example 1-2) are shown in Table 1 together with other results.

Next, the yarn, whose moisture content was adjusted and deposited on the net-fun pair, was unwound and subjected to high-tension drying. As the high-tension drying device (11 in FIG. 1), a pair of heated rollers that can be heated with steam were used, and Nelson rollers were used at the front and rear for applying tension. In addition, in order to efficiently perform drying, that is, to reduce the moisture content, the heated roller was surrounded to create a heated atmosphere. The number of times the fibers were wound around the heated roller was adjusted so that the fibers remained in the high tension dryer for about 15 to 20 seconds. The tension was applied by adjusting the rotational speed ratio of the Nelson roller on the inlet side and the Nelson roller 2- on the outlet side. The temperature and tension of the heated roller, and the moisture content of the wound fibers are shown in Table 1, along with various properties of the wound fibers.

Incidentally, all the fiber ores shown in Table 1 had a summer-type crystal form.

According to Table 1, when the moisture content before high-tension drying is 20 to 80% by weight, it can be seen that high strength, high modulus, and a large temperature coefficient of strength are obtained, indicating that impact strength is large. I can do it.

Comparative Example 2 A supplementary test of f-1 of Example 2 of JP-A No. 47-43419 was carried out.

Prepare PPTA with a logarithmic viscosity of 6.6 di/Jil,
Mix with 99.7% concentrated sulfuric acid to make 20%! A spinneret (100 holes with a diameter of 0.06 m) was prepared at 85 °C.
) It was then extruded into air and introduced into water at 3°C to solidify.

The yarn taken out from the coagulation bath is wound on a devin, and then soaked in water and then 0.
．． It was washed with IN NaHCOs, water at 70° C., and dried. Heat treatment under tension of 6.5 Fi/denier 35
The test was carried out at 0°C for 1.5 seconds.

The obtained fiber had a large apparent crystallite size of 80X, a single fiber strength of 311/denier, and a single fiber modulus of 88,017 denier, but the temperature coefficient of strength was 1.
It was smaller than the fibers of 01 and Example 1.

Comparative Example 3 A supplementary test of Example 1 of JP-A-53-98415 was carried out for comparison.

PPTA with logarithmic viscosity 3.5 dV71 and 99.5% by weight
of concentrated sulfuric acid and an optically anisotropic dope of 18.1 wt.
After preparing at 5°C and degassing, the spinneret (
The yarn is extruded into the air through 100 holes with a diameter of 0.07 m, and then introduced into a coagulation bath (30 wt% sulfuric acid aqueous solution at 2°C) located 5 m below the spinneret to coagulate. I rolled it up and washed it with water. The water-washed fibers are 11
This fiber was heat-treated for 30 seconds at a moisture content of 3x i% while being stretched 1.05 times (tension: approximately 119/denier) in nitrogen gas at 140°C.

The obtained fiber had a single fiber strength of 22 g/denier, a single fiber modulus of 79011/denier, and an apparent microcrystal size of 58×1 strength temperature coefficient of 0.89.

Comparative Example 4 A follow-up test of Example 2-1 of JP-A-59-47421 was carried out for comparison.

A sulfuric acid aqueous solution was added through a 5 m space from a spinneret (100 holes with a diameter of 0.06 m) to add a 20 wt% dope from PPTA with a logarithmic viscosity of 6.5 di/11 and 99.5 wt% concentrated sulfuric acid. (A0% by weight, ~5°C), and the yarn taken out from the coagulation bath was 1.2 g/
After applying denier tension, it was thrown onto a net conveyor, washed with water, and dried.

The obtained fiber had a high single fiber strength of 28 I/denier and a single R rough modulus of 75011/denier, but a small temperature coefficient of strength of 0.86.

Example 2 Using PPTA with a logarithmic viscosity of 6.4, 99.9% by weight sulfuric acid, a polymer concentration of 19.5% by weight was obtained using approximately 8%
The optically anisotropic dogu was obtained by melting at 0-85°C and then degassed to a vacuum of 0.5-0.2 sw Hg over a period of about 5 hours. Spinning was carried out using a spinneret (500 holes with a diameter of 0.061111 mm) at a temperature of about 85° C., an air layer thickness of 10 flies, a draft of 67° C., and a coagulation bath of 10° C. water.

The fibers taken out from the coagulation bath were thrown onto a net conveyor so that only a tension of about 0.1519/denier was applied to create a fiber, and in that state, a 5% caustic soda aqueous solution and water were sequentially poured over it for about 30 minutes. Washed.

The washed fibers had a moisture content of about 280% by weight, so first a vacuum suction port was installed below the processing conveyor to remove the water to a moisture content of about 90% by weight.
It was passed through a heating box at 0° C. to give a moisture content of 53% by weight.

Example 1 The fibers whose moisture content was adjusted on a net conveyor were
8I! The film was dried at 140° C. for about 18 seconds under a tension of /denier and rolled up. The rolled fiber has a water content of 09%, a ■-type crystal shape, a logarithmic viscosity of 6.1 dl/I, and an apparent microcrystal size of 49X.
, density 1.4517 cm", crystal orientation angle 10', single fiber elongation 2.9 inches, single fiber modulus 890 #/denier, single fiber strength 33 I/denier, temperature coefficient of strength 1.1
It was 8.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the fiber manufacturing method of the present invention. 1&... coagulation liquid, 1b... coagulation bath, 2... spinneret, 3m, 3b, 3e, 3d... fiber thread, 4
...Take-out roller, 5...Transfer roller, 6...
・Reversing conveyor, 7... Processing conveyor, 8... Water washing device, 9... Direction changing roller, 10.7 minute adjustment device,
10m, 10b. 10 e * 10 d? 10 e... Moisture control device block, 11... High tension drying device, 12...
・Cover belt, 13... Winding machine, t... Coagulation liquid depth. Figure 2 shows a diffraction intensity curve on the equatorial line in X-ray diffraction of u/su (p-phenylene terephthalamide) fiber.

Claims (1)

[Claims] 1. Fibers having type I crystals and consisting essentially of poly(p-phenylene terephthalamide) having a logarithmic viscosity of 5.0 dl/g or more, comprising the following (A) to (G): A high modulus fiber that satisfies all of the following. (A) Apparent microcrystal size = 35-55 Å (B) Density ≧1.43 g/cm^3 (C) Crystal orientation angle ≦14 degrees (D) Single fiber elongation ≦3.3% (E) Single fiber modulus ≧750 g/Denier (F) Single fiber strength ≧25 g/Denier (G) Temperature coefficient of strength ≧1.05 2. Poly(p-phenylene terephthalamide) with a logarithmic viscosity of 5.0 dl/g or more 97 A dope obtained by dissolving in concentrated sulfuric acid of ~101% by weight to a polymer concentration of 17 to 20% by weight was passed through a spinneret into a gas, and then heated to -10% by weight.
After extruding and coagulating the yarn into a coagulating liquid at ℃ to 25℃, the yarn is deposited on a net conveyor and washed, and then the moisture content of the yarn is reduced to 20 to 80% by weight on the net conveyor.
Then, the yarn is subjected to a tension of 5 to 15 g/denier (however, the denier is based on the fiber after drying) until the moisture content reaches 0.1 to 1.5% by weight. 5
A method for producing high modulus fiber characterized by drying at 0 to 180°C.