JPH0246688B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high modulus type poly(p-phenylene terephthalamide) (hereinafter sometimes abbreviated as PPTA) fiber and a method for producing the same. Specifically, this article 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 plastics and the like. Prior Art It is known that high-strength, high-modulus fibers can be obtained from PPTA (for example, JP-A-47-39458 and JP-A-47-43419). Of these,
JP-A-47-39458 basically discloses a medium modulus type fiber, which is used in a field different from the high modulus type fiber which is the subject of the present invention. On the other hand, JP-A-47-43419
The publication discloses that a high modulus type PPTA fiber can be obtained by performing air discharge wet spinning from a high concentration PPTA dope and then subjecting it to tension heat treatment. Kevlar 49 is commercially available 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,
49-110913, JP 52-12325, JP 52-12326, JP 55-1324,
(Japanese Unexamined Patent Publication No. 55-122011), most of them are due to tension heat treatment accompanied by stretching, and according to the knowledge obtained by the present inventors, the above-mentioned drawback of low impact strength is completely eliminated. Not improved. In addition, it also has the disadvantage that thermal deterioration and increase in fuzz are difficult to avoid. On the other hand, several methods have been proposed for producing high modulus PPTA fibers without stress heat treatment. For example, JP-A-53-98145
The publication discloses a method of drawing wet fibers in an inert gas at a temperature below 200°C. but,
In this method, the starting fibers retain a considerable amount of sulfuric acid and contain 130 to 140% moisture, making them susceptible to thermal deterioration, and therefore requiring the use of expensive inert gases. The idea of having both high strength and high modulus is not realized because the strength is low, and the fibers shown in the examples have relatively high impact strength, probably because unnecessary tension is applied during the washing process and the initial drying process. There are flaws such as being weak in Also, in Japanese Patent Application Laid-Open No. 59-47421,
It has been described that high modulus fibers can be obtained by applying tension during a specific coagulation state. However, the fibers obtained by this method have insufficient impact strength. Furthermore, JP-A No. 47-39458 discloses Example 1 which shows the hot stretching method for reference.
In addition to the last part of the description, fibers with relatively large as-spun moduli are exemplified (eg Examples 1, 3g, 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, the present invention aims to solve the above problems of the prior art. This is an epoch-making product that combines high impact strength with high impact strength. And, such highly desirable fibers have certain novel structural properties and are produced by a new and specific manufacturing process, i.e., air gap spinning of highly concentrated dope of PPTA with a high degree of polymerization, and with as low as possible 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 reached. The present inventor completed the present invention based on this discovery. Means for Solving the Problems That is, the first aspect of the present invention is a fiber having a type crystal and consisting essentially of poly(p-phenylene terephthalamide) having a logarithmic viscosity of 5.0 dl/g or more, A high modulus fiber that satisfies all of the following (A) to (G). (A) Apparent microcrystal size = 35 to 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 ≧ 750g/denier (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 dl/g or more. The dope obtained by dissolving in concentrated sulfuric acid of 97 to 101% by weight to a polymer concentration of 17 to 20% by weight is extruded through a spinneret into a gas and then into a coagulation liquid at -10°C to 25°C. te 0.5
g/denier (however, the denier is based on the fiber after drying) The yarn coagulated under a tension of less than 20~80
% by weight, and then the yarn is heated under a tension of 5 to 15 g/denier (however, the denier is based on the fiber after drying) until the water content reaches 0.1 to 1.5 weight %. A method for producing high modulus fiber characterized by drying at 180°C. The polymer used in the present invention consists essentially of PPTA. Here, "substantially" means:
Polymers other than PPTA [e.g., poly-(m-phenylene terephthalamide), poly-(p-phenylene isophthalamide) ), poly(m-phenylene isophthalamide), poly(polymethylene terephthalamide, aliphatic polyamide, alicyclic polyamide, polyester, polyimide, polyurethane, polyurea, etc.) are blended, or PPTA is blended with other polymers. units (e.g., nuclear substituted p-phenylene units, nuclear substituted or unsubstituted biphenylene units, p-phenylene units, m-phenylene units,
(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, ultraviolet 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/g, more preferably 5.5 dl/g or more, and still more preferably
Logarithmic viscosity of 6.0 dl/g or more (0.5 in concentrated sulfuric acid at 25°C)
(measured in g/dl). A high logarithmic viscosity means a high degree of polymerization and is associated with high fiber strength. 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 dl/g, and therefore has a small strength. The fiber of the present invention has a crystal form of the so-called type.
Should consist of PPTA. Here PPTA
To explain a little about the crystalline form of fibers, Kevlar and Kevlar 49, which are on the market, or PPTA manufactured by the method described in JP-A No. 47-39458, for example.
When the crystal structure of the fibers is examined by X-ray diffraction, without exception, large diffraction peaks are seen at 2θ≒23 degrees and 2θ≒21 degrees on the equator line (Figure 2, A).
According to the definition of Takayanagi et al. [J.Appl.Polym.Sci., vol. 23, p. 915 (1979)], it can be said to be a type crystal. Takayanagi et al. have proposed another crystalline form of PPTA. In the production of PPTA film, it is said that depending on the choice of coagulant, type or type of crystals may occur.
There is no mention of fibers. Next, we will discuss types and how to determine them. Using a conventional method, the PPTA fiber sample is irradiated with X-rays from a direction perpendicular to the fiber length direction to obtain a diffraction pattern. Pay attention to the diffraction peak in the equatorial direction of the diffraction pattern (e.g.
Record the diffraction intensity on the equator line in the range of 2θ≒16~30°). At this time, in addition to the large diffraction peak at 2θ≒23°, the one with a diffraction peak at 2θ≒21° (A in Figure 2) is the type crystal, and the one with a diffraction peak at 2θ≒18° (Fig. (b) are respectively defined as type crystals. Note that when the types are mixed, diffraction peaks at both 2θ≒18° and 2θ≒21° will be observed. The relationship between fiber crystal form and fiber properties cannot be directly understood. However, type crystals are formed at low coagulation bath temperatures below -15℃,
When coagulating at such temperatures, the viscosity of the coagulation bath increases, so considerable tension is often applied to the coagulated threads, making it difficult to increase the strength or
This is undesirable because the impact strength is insufficient and fuzz and so-called single yarn breakage tend to occur frequently. In the present invention, all or most of the
The subject is PPTA fiber. The fiber of the present invention has an X-ray diffraction peak of 35 to 22 degrees, as measured by the method described in JP-A-55-122012.
It has an apparent crystallite size of 55 Å. This requirement is closely related to the fact that the fibers of the present invention are very high modulus fibers, yet have improved impact resistance. Furthermore, it is associated with other characteristics such as less fibrillation and greater nodule strength. The apparent size of microcrystals is preferably 40 to 55 Å, more preferably 45 to 52 Å. In this way, in order to have a relatively small crystallite size for a high modulus PPTA fiber, it is necessary to use a method that performs the molecular chain orientation necessary for high modulus at a low temperature. In other words, the fibers of the present invention are dried under high tension at 180°C or lower from a moisture content of 20 to 80% by weight to a moisture content of 0.1 to 1.5% by weight, thereby increasing the orientation of molecular chains. Most of the conventional techniques disclosing high modulus PPTA fibers, for example, JP-A No. 47-43419, JP-A No. 47-43419, Publication No. 49-110913, JP-A-52-12325
Publication No. 12326, Japanese Patent Application Laid-Open No. 1983-
It can be distinguished from the fibers obtained by the method of JP-A No. 1324 and JP-A-52-122011, in which tension heat treatment accompanied by stretching is performed at high temperature after drying. The fibers of the invention should have a density of at least 1.43 g/m ³ . If the density is less than 1.43 g/cm ³ , it indicates that the fiber contains many cracks and voids, has extremely low crystallinity, or has a non-uniform aggregated structure. Its low strength reduces its practical value. Such low density fibers may be obtained, for example, by wet spinning directly from a spinneret into a coagulation bath, with very low draft or polymer concentration. The density of the PPTA fiber 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 g/cm ³ due to their disordered agglomerated structure, low strength, and extremely low knot strength. small. The fibers of the present invention 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 high modulus for PPTA fibers that do not meet this requirement. The crystal orientation angle is preferably
It is 13° or less, more preferably 11° or less.
Fibers with a crystal orientation angle of 14° or less can be obtained by so-called gap spinning followed by high tension treatment in the subsequent drying stage. The fibers of the present invention also have a single fiber elongation of 3.3% or less. Single fiber elongation is measured according to the measurement method of Japanese Patent Application Laid-Open No. 47-39458 for single fibers. However, in the method described in the same publication, since the length of the measuring part is as short as 1 inch, slippage in the gripping part of the sample often causes errors. For this reason, for example,
It is desirable to confirm the true elongation using the method described in ASTMD1906-62T. The fiber of the present invention has the above-mentioned limitations on single fiber elongation.
It can be clearly distinguished from the fiber of Publication No. 39458. Furthermore, since the fiber of the present invention has a single fiber modulus of 750 g/denier or more, the fiber of the present invention can be used as a reinforcing fiber for plastics, rubber, etc., especially for composites that require excellent deformation resistance. When used as reinforcing fibers for wood, it creates tremendous value. The monofilament modulus of the present invention is
Measurement is performed by changing the gripping length of the sample to 20 cm in the method described in Japanese Patent Application Laid-Open No. 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 will be large, as described above. The fibers of the present invention preferably have a single fiber modulus of 800 g/denier or higher. The fiber of the present invention has a strength of 25 g/denier or more when measured as a single fiber. The strength can be measured by the method disclosed in Japanese Patent Application Laid-Open No. 47-39458. 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 g/denier or more is more useful, and a single fiber strength of 30 g/denier or more is most useful. The reason why the fiber of the present invention has high modulus and high strength is that it is made of PPTA with a high degree of polymerization, and it is also necessary to apply tension in the late stage of drying in order to highly orient the molecular chains during the spinning process. This is because there are very few cracks, voids, etc. that can reduce strength, as the other processes before coagulation, water washing, and drying are carried out without tension or at the lowest possible level. It is thought that. In this regard, the PPTA fibers disclosed in the examples of JP-A No. 53-98415 have a relatively low degree of polymerization, as well as the fact that a slight tension is applied during the water washing process, and the moisture content is 130 to 140%. The strength is somewhat low due to the fact that high tension is applied while drying. 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 refers to the number obtained by dividing the single fiber strength measured at -35°C by the single fiber strength measured at 20°C, and for the fiber of the present invention, it is 1.05 or more, preferably 1.10 or more. The impact strength of fibers is generally
This is the strength when the fiber is subjected to rapid deformation, for example, rapid tensile deformation, so it is the strength when the fiber is subjected to deformation in which the time for deformation is shorter than the time for movement of the polymer molecular chains. Therefore, by making the molecular chains less mobile, that is, at a lower 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, and the larger this value is, the better the impact strength of the fiber is. To the best of the knowledge of the present inventors, there is no known fiber having a single fiber strength of 25 g/denier or more, a single fiber modulus of 750 g/denier or more, and a temperature coefficient of strength of 1.05 or more. It is processed by hot stretching at a high temperature of approximately 200℃ or higher, by applying tension during the initial stage of the washing process and drying process,
Alternatively, if tension is applied during solidification, it is possible to create a high modulus fiber by increasing the orientation of the molecular chains, but this often results in a decrease in strength, and the temperature coefficient of strength is always 1.05.
This is because it will be less than That is, the fiber of the present invention is
High tension is applied to the fibers at low temperatures concentrated in the late drying period when molecular chain orientation can be most effectively achieved without causing relaxation, while other processes are less effective in promoting molecular chain orientation. This can only be achieved by using a special manufacturing method that applies no tension or only the minimum possible tension to the fibers. The thickness of the fiber of the present invention is not particularly limited, but a single fiber of 0.1 to 5 deniers is usually useful. The number of filaments is not particularly limited either, and may be used in the form of monofilament, 10,000 or more yarns, cords, woven fabrics, chopped strands, fibers, and the like.
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 extremely good modulus and are useful as reinforcing fibers for plastics, rubber, etc., and especially as reinforcing fibers for composite materials that require high deformation resistance. In such applications, this fiber has superior impact resistance compared to known high modulus fibers, such as the fiber disclosed in JP-A-47-43419 and the commercially available Kevlar 49. It is particularly useful as a reinforcing fiber for composite materials that require such performance. The fiber of the present invention also has the characteristics of being difficult to fibrillate and can be manufactured at low cost, and has 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 having a logarithmic viscosity of 5.0 dl/g or more in concentrated sulfuric acid of 97 to 101% by weight to a polymer concentration of 17 to 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 PPTA to be charged should be determined with this point in mind. In the fiber of the present invention, in order to ensure the desired level of physical properties,
It is preferable to use PPTA having a logarithmic viscosity of about 5.2 dl/g or more. As a solvent for dope preparation used in spinning, 97
Concentrated sulfuric acid at a concentration of ~101% by weight, preferably 98.5-100.5%, most preferably 99.8-1001% by weight is used. Specifically, the concentration should be appropriately selected depending on the logarithmic viscosity of the polymer and the concentration of the polymer dissolved in the dope used for spinning. When the concentration of concentrated sulfuric acid 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. Conversely,
If the concentrated sulfuric acid concentration exceeds 101% by weight, ie, fuming sulfuric acid containing a large excess of SO ₃ , it is difficult to handle, and moreover, the polymer hardly dissolves.
For fuming sulfuric acid at a concentration below 101% with a small excess of _SO3 ,
It is known that the polymer has good solubility and provides a preferred spinning dope. However, the presence of a large excess of SO ₃ in concentrated sulfuric acid causes large voids in the internal structure of the resulting fibers, thus reducing the density of the fibers and also resulting in a dull appearance and poor mechanical properties. This results in drawbacks such as lowering the maximum possible withdrawal speed from the coagulation bath. The dope used for spinning is used to achieve high modulus.
It is necessary to prepare it so that it contains 17% by weight or more of poly(p-phenylene terephthalamide).
Furthermore, in the case of PPTA with a high degree of polymerization having a logarithmic viscosity of more than 5.0 dl/g, it is difficult to dissolve it in concentrated sulfuric acid in an amount exceeding 20% by weight. From the point of view of producing high-strength, high-modulus fibers, the polymer concentration is
More preferably, it is 19 to 20% by weight. The temperature of the spinning dope is preferably any temperature between about 100° C. and the lowest temperature at which the dope exhibits optical anisotropy and has sufficient fluidity to be handleable. Specifically, the temperature of the spinning dope depends on the polymer concentration, sulfuric acid concentration, spinneret orifice diameter,
It is determined as appropriate, taking into account the discharge linear velocity and the like. The dope thus prepared is extruded through a spinneret into a gas and then into a coagulation bath. It may be advantageous, especially for industrial production, to degas, filter and meter the dope before passing it through the spinneret. There are no particular restrictions on the shape, number of holes, size of holes, etc. of the thread cap. The diameter of the hole is usually 0.01 to 0.5 mm.
The linear speed of the dope extruded from the spinneret is not particularly limited either, 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 the spinneret is suddenly extruded into the coagulation bath without passing gas, the draft is 1.5
This is because it is difficult to make the fibers larger and the resulting fibers have low density and strength. Examples of the gas include air, nitrogen, argon, oxygen, etc. Air is most preferred from the viewpoint of economy, operability, etc. The thickness of the gas, ie, the distance between the spinneret and the coagulation surface, is suitably about 0.2 to 50 cm. The dope flow released into the gas is
It then needs to be extruded into a coagulation bath where it undergoes coagulation. The coagulation liquid should be kept within the temperature range of -10°C to 25°C. If the temperature of the coagulating liquid exceeds 25°C, the density of the fibers may decrease or the strength may become less than 25 g/denier, which is not preferable. Additionally, when the temperature of the coagulating liquid drops below -10°C, the viscosity of the coagulating liquid generally increases, making it unavoidable that a high tension is applied to the coagulated yarn during spinning, as well as decreasing the coagulating speed 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. In addition, when coagulating at a temperature lower than -10°C, PPTA fibers having a type crystal form are produced, whereas at a temperature of -10°C or higher, all or most of the fibers become the type crystal form, which is not suitable for the present invention. of fibers are 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 isopropanol, or mixtures of water and the above-mentioned alcohols,
Alternatively, an aqueous solution of an acid such as sulfuric acid, an aqueous alkali solution such as ammonium hydroxide, or an aqueous solution of various salts such as calcium chloride may be 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 preferable to use a so-called funnel-shaped coagulation bath in which the coagulation liquid 1a falls together with the running yarn, as shown in 1b of FIG. Preferably, such a coagulation bath is also preferred in terms of maintaining the spinning speed at a high level in industrial production. It is also preferable to make the depth of the coagulation liquid (l in FIG. 1) as small as possible because this reduces the tension on the coagulated filament. Generally, the lower the tension applied to the coagulated yarn, the greater the strength of the fiber and the better the sag strength. The coagulation bath may have two or more stages if necessary. The draft in spinning is usually selected in the range of 2 to 15, preferably 3 to 10, depending on the thickness of the gas layer, the diameter of the spinneret, the polymer concentration, the logarithmic viscosity of the polymer, etc. If the draft is too small, the orientation of the molecular chains tends to be insufficient.
A considerable degree of compensation can be achieved by applying tension during the late 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 dope 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, JP-A No. 59-47421
In the publication, 1 to 4 g/g of coagulation bath and coagulated thread
Although it is disclosed that high-modulus fibers can be obtained by increasing the molecular chain orientation by applying denier tension, this method inevitably has the disadvantage that the impact resistance of the obtained fibers decreases. In the present invention, the yarn leaving the coagulation bath is approximately 0.5 g/denier (denier is based on the fiber after washing and drying).
It is necessary to provide no more than a tension, preferably no more than 0.3 g/denier, most preferably no more than 0.2 g/denier. The coagulated threads drawn from the coagulation bath must be deposited on a net conveyor for cleaning. 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, JP-A-53-
Although Publication No. 98415 states that it is generally possible to wash the coagulated yarn on a net conveyor, all of the examples are carried out on rollers under a constant tension, and this paper does not The temperature coefficient of strength is smaller than that of the inventive fiber. 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 as much sulfuric acid 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 net conveyor that is not under any tension. 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 is, so that by any method such as drying or suction, the water content is 20 to 80% by weight, preferably 30 to 70% by weight. % moisture content. For drying, the temperature is room temperature to approximately 200℃
Hot air, hot plates, dielectric heating, infrared heaters, etc. can be used. In the present invention, it is very important to adjust the moisture content to 20-80% by weight before performing high tension drying. This is because even if high tension is applied to fibers with a water content of over 80% by weight, the molecular chains will not be oriented efficiently.
In other words, since a considerable degree of orientation relaxation occurs, microscopic destruction of the fiber structure progresses, resulting in a decrease in impact strength.In addition, in industrial production, tension drying results in a loss of thermal energy due to the low degree of fiber aggregation. This is because it becomes large and disadvantageous. 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 re-wetted. The fibers are adjusted to have a moisture content of 20-80% by weight on a net conveyor, and are unwound under a tension of 5-15g/denier at a temperature of 50-180℃ until the moisture content is 0.1-1.5% by weight. dried. The drying tension is preferably 5 to 12 g/denier, based on the fiber after drying. When a tension of 5 to 15 g/denier is applied, the fibers are drawn by about 2 to 8%. 5
High modulus cannot be achieved at tensions below g/denier. 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 50 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 exceed 55 Å due to excessive crystal growth. The drying humidity is preferably 100 to 150°C. The time for high-tension drying may be determined by taking into consideration the denier of the fiber, the number of filaments, the capacity of the heat source, the heat transfer efficiency, etc. so that the moisture content of the fiber at the end of drying is 0.1 to 1.5% by weight. 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 molecular chain orientation may occur, and the modulus may reach an insufficient level. on the other hand,
Applying tension to a moisture content of less than 0.1% by weight is
Not only is this unfavorable in terms of energy loss, but also the occurrence of fuzz increases and the apparent size of the microcrystals exceeds 55 Å, thus losing the characteristics of the fiber of the present invention. The moisture content after high tension drying is preferably 0.3 to 1.2% by weight. The method and device 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. Fig. 1 shows an embodiment in which high tension drying is carried out directly after moisture adjustment, and this method is preferable because it can be carried out industrially efficiently. It is also possible to wind up the fibers and dry them again batchwise or semi-continuously under high tension. The atmosphere during drying is determined from the viewpoint of cost and simplicity.
It is usually carried out in air, 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 applies 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, and causes a high degree of molecular chain orientation. The fiber of the present invention is a new PPTA fiber with unique properties obtained through this new and unprecedented technical idea of never applying unnecessary tension during the process. Therefore, the feature of the present invention is the first
In addition to having high strength and high modulus, the fibers also have high impact strength, which is why the conventionally known high modulus type PPTA
This is a big difference from fiber. 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 rubbers 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 thereto, and can be used in monofilaments, roving yarns, fabrics, and yarns. It can also be used as rope, reinforcing material for woven fabrics, plastics, metals, cement, ceramics, etc., in the form of rolled strands, and as cotton. Example 1 and Comparative 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 made using the apparatus shown in Figure 1. PPTA to 99.8% sulfuric acid with polymer concentration of 19% by weight
The mixture was melted at 75° C. and degassed under reduced pressure for about 2 hours. While filtering the dope exhibiting optical anisotropy maintained at 75 to 80°C, it is extruded through a spinneret (2 in Figure 1) having 100 pores with a diameter of 0.065 mm to form a material with approximately 5 mm diameter.
After running in the air, it was extruded into a 30% by weight sulfuric acid aqueous solution 1a maintained at -5°C. Draft 8
The coagulated thread was removed from the coagulation bath at a speed of 300 m/min. The coagulated yarn was taken out and placed on a net conveyor 7 so that only a tension of about 0.18 g/denier (denier is based on dry fiber) was applied to the coagulated yarn. The accumulated threads were first washed with water, then with a dilute aqueous solution of caustic soda, and then again with water so that the residual sulfuric acid was 80 ppm or less relative to the fibers, and then sprinkled with an oil agent (the oil agent application device is shown in Figure 1). (not shown), then the moisture regulator (1 in Figure 1).
The moisture content of the fibers (yarns) deposited in step 0) was adjusted. The moisture regulating device has a length of approximately 2.5 m and is divided into five blocks 10a to 10d as shown in Fig. 1, and each block is independently controlled at approximately 120°C.
The structure was such that hot air heated by water vapor was blown into the tank. When all five blocks were operated at about 120°C (Comparative Example 1-1), when the other four blocks except 10a were operated at about 120°C (Example 1-1), and when all the other blocks except 10a and 10b were operated at about 120°C, When the three blocks were operated at about 120°C (Example 1-2), 1
When only 0d and 10e were operated at about 120°C (Example 1-3), when only 10e was operated at about 120°C (Example 1-4), when all blocks were left at room temperature without heating. The results of the moisture content of (Comparative Example 1-2) are shown in Table 1 together with other results. Next, the yarn with its moisture content adjusted and deposited on the net conveyor 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, a heated atmosphere was created by surrounding the heated roller. The number of times the fibers were wrapped 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 on the outlet side. heat roller temperature,
The tension and moisture content of the wound fibers are shown in Table 1 along with various properties of the wound fibers. Incidentally, all the fibers shown in Table 1 had the same type of crystal form. From Table 1, it can be seen that when the moisture content before high-tension drying is 20 to 80% by weight, the product has high strength, high modulus, and a large temperature coefficient of strength, which indicates that the impact strength is large.

[Table] Note: Change in moisture content means the change in moisture content before and after high-tension drying.
Comparative Example 2 A follow-up test was carried out on f-1 of Example 2 of JP-A-47-43419. Prepare PPTA with logarithmic viscosity 6.6 dl/g, 99.7%
Mix with concentrated sulfuric acid to make a 20% by weight dope, 85
It was extruded into air through a spinneret (100 holes with a diameter of 0.06 mm) at 3°C, and then introduced into water at 3°C to coagulate. The yarn taken out from the coagulation bath is wound onto a bobbin, and then soaked in water and then
It was washed with 0.1N NaHCO ₃ and further with water at 70°C, and dried. Heat treatment at 350℃ under tension of 6.5g/denier
It lasted 1.5 seconds. The obtained fiber has an apparent microcrystal size of 80
The fiber had a large single fiber strength of 31 g/denier and a single fiber modulus of 880 g/denier, but the temperature coefficient of strength was 1.01, which was smaller than the fiber of Example 1. Comparative Example 3 A supplementary test of Example 1 of JP-A-53-98415 was conducted for comparison. An optically anisotropic dope of 18.1% by weight was prepared from PPTA with a logarithmic viscosity of 3.5dl/g and 99.5% by weight of concentrated sulfuric acid at 75°C.
After degassing, extrusion into air through a spinneret (100 holes with a diameter of 0.07 mm), followed by a coagulation bath (at 2°C) located 55 mm below the spinneret.
(30% by weight aqueous sulfuric acid solution) for coagulation, and the taken out yarn was wound around a Nelson roller and washed with water. The water-washed fiber has a moisture content of 113% by weight.
Stretched 1.05 times in nitrogen gas at 140℃ (tension is approximately 11
g/denier) for 30 seconds. The obtained fiber had a single fiber strength of 22 g/denier,
The single fiber modulus was 790 g/denier, the apparent crystallite size was 58 Å, and the temperature coefficient of strength was 0.89. Comparative Example 4 A supplementary test of Example 2-1 of JP-A-59-47421 was carried out for comparison. A 20% by weight dope was made from PPTA with a logarithmic viscosity of 6.5 dl/g and 99.5% by weight concentrated sulfuric acid, and a sulfuric acid aqueous solution (40% by weight, - extrude to 5℃),
The yarn taken out from the coagulation bath is passed between a pair of rollers.
After applying a tension of 1.2 g/denier, it was thrown onto a net conveyor, washed with water, and dried. The obtained fiber had a single fiber strength of 28 g/denier,
Although the single fiber modulus was large at 750 g/denier, the temperature coefficient of strength was small at 0.86. Example 2 Using PPTA with a logarithmic viscosity of 6.4 and 99.9% by weight sulfuric acid, the polymer concentration was approximately 19.5% by weight.
The optically anisotropic dope was obtained by melting at 80 to 85°C, and then degassed by reducing the pressure to 0.5 to 0.2 mmHg over about 5 hours. Spinning was carried out using a spinneret (500 holes with a diameter of 0.06 mm) at a temperature of approximately 85°C, an air layer thickness of 10 mm, a draft of 6.7, and a coagulation bath of water at 10°C. The fibers taken out from the coagulation bath were thrown onto a net conveyor so that the tension was only about 0.15 g/denier to form a thread pile, and in this state, a 5% aqueous solution of caustic soda and water were successively sprinkled on the fibers and washed for about 30 minutes. The washed fibers had a moisture content of approximately 280% by weight, so first a vacuum suction port was installed below the processing conveyor to remove the water to a moisture content of approximately 90% by weight, and then the fibers were heated to 100°C. was passed through a heating box to give a moisture content of 53% by weight. The fibers with their moisture content adjusted on the net conveyor are
It was introduced into the same high tension drying device as in Example 1 and dried at 140°C for about 18 seconds under a tension of 8 g/denier.
I rolled it up. The rolled fiber has a water content of 0.9%, a type I crystal, a logarithmic viscosity of 6.1 dl/g, an apparent crystallite size of 49 Å, a density of 1.45 g/cm ³ , and a crystal orientation angle.
10°, single fiber elongation 2.9%, single fiber modulus 890
g/denier, single fiber strength 33 g/denier, and temperature coefficient of strength 1.18.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the fiber manufacturing method of the present invention. 1a... Coagulation liquid, 1b... Coagulation bath, 2... Spinneret, 3a, 3b, 3c, 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... Moisture adjustment device, 10a, 10b, 10c, 10d, 10e
. . . Moisture adjustment device block, 11 . . . High tension drying device, 12 . . . Cover belt, 13 . FIG. 2 shows a diffraction intensity curve on the equatorial line in X-ray diffraction of poly(p-phenylene terephthalamide) fiber.

Claims (1)

[Scope of Claims] A fiber consisting essentially of poly(p-phenylene terephthalamide) having type 1 crystals and having a logarithmic viscosity of 5.0 dl/g or more, which comprises all of the following (A) to (G): High modulus fiber that satisfies the following. (A) Apparent microcrystal size = 35 to 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 ≧ 750g/denier (F) Single fiber strength ≦25g/denier (G) Temperature coefficient of strength ≧1.05 2 Poly(p-phenylene terephthalamide) with a logarithmic viscosity of 5.0 dl/g or more is dissolved in 97 to 101% by weight concentrated sulfuric acid The dope obtained by dissolving the polymer to a concentration of 17 to 20% by weight is poured into a gas through a spinneret.
Then extrude into coagulation liquid at -10℃~25℃ to give 0.5
g/denier (however, the denier is based on the fiber after drying) The yarn coagulated under a tension of less than 20~80
% by weight, and then the yarn is heated under a tension of 5 to 15 g/denier (however, the denier is based on the fiber after drying) until the water content reaches 0.1 to 1.5 weight %. A manufacturing method for high modulus fibers that is characterized by drying at 180℃.