JPH0434022A - Preparation of aramide fiber - Google Patents

Abstract

PURPOSE:To improve the compression characteristics of an aramide fiber by releasing the tension of the fiber when coagulated and simultaneously bringing the fiber into contact with a silicon alkoxide solution, when a solution of para- oriented aromatic polyamide in sulfuric acid is extruded into a coagulating bath through air, washed with water and subsequently dried to provide the polyamide fiber. CONSTITUTION:In a method for preparing a para-oriented aromatic polyamide fiber by dissolving a para-oriented aromatic polyamide in 95-101 wt.% concentrated sulfuric acid in a concentration of >=15wt.%, extruding the solution into a coagulating bath through air, washing the fiber with water and subsequently drying the fiber, the tension of the fiber in the coagulating process or in the early washing process wherein the fiber contains the sulfuric acid in a concentration of >=5wt.% is released by releasing the fiber on a conveyor, etc. The fiber having a water content of >=80wt.% is brought into contact with a silicon alkoxide solution and subsequently dried at a temperature of >=200 deg.C to prepare the para-oriented aromatic polyamide fiber containing silica in a concentration of 0.5-10wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing para-oriented aromatic polyamide fibers. More specifically, the present invention relates to a method for producing high-performance para-oriented aromatic polyamide fibers with improved compression properties.

[Conventional technology]

Conventionally, para-oriented aromatic polyamide fibers have been used as polymeric materials with high specific strength, specific modulus, and excellent heat resistance to make ropes, cables, cords, etc., and also with thermoplastic or thermosetting resin as a matrix. fiber-reinforced resin,
Its use as a reinforcing material for rubber, etc. is being considered.

This fiber material achieves high strength and high elastic modulus in the fiber axis (tensile direction) by orienting the molecular chains in the fiber axis direction by liquid crystal spinning rigid molecules under specific conditions. ing. However, a disadvantage of fibers such as those in which the molecular chains are extremely uniaxially oriented is that they tend to fibrillate along the fiber axis and are susceptible to cracking in the radial direction of the fiber axis.

Therefore, although the tensile strength is high, the compressive strength is extremely low compared to the tensile strength.

Therefore, fatigue properties in applications where the compression mode is included in the fatigue process are not necessarily good, and careful attention must be paid when designing the material. However, no effective method for improving the compression properties of these aramid fibers has been disclosed. On the other hand, as a method for improving bending fatigue properties that include the compression mode, it is not a direct method of improving compression properties, but it is possible to increase elongation by relaxation heat treatment (Japanese Patent Laid-Open No. 5
5-122612), a method for improving fibrillation by surface modification (Japanese Patent Application Laid-open No. 62-243620),
It is only disclosed.

[Problem to be solved by the invention]

The present invention was made in order to improve such drawbacks, that is, compression properties, and its purpose is to provide a method for industrially producing high-performance para-oriented aromatic polyamide fibers with excellent compression properties. It's about trying.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present inventors have conducted intensive research and found that a silica-containing para-oriented aromatic polyamide obtained by impregnating a specific amount of silicon alkoxide into fibers under specific conditions and then heat-treating the fibers. The present invention was achieved by discovering that fibers have excellent compression properties.

That is, the present invention provides para-oriented aromatic polyamide at a concentration of 95% to
An optically anisotropic dope dissolved in 101% by weight concentrated sulfuric acid,
After extruding the yarn through an orifice into the air and then into a coagulation bath, the yarn is pulled out from the coagulation bath, washed with water,
In the method for producing para-oriented aromatic polyamide fibers that are dried, the tension is substantially released from the coagulated yarn during coagulation or at the initial stage of washing containing 5% by weight or more of sulfuric acid per dry fiber, and the moisture content is reduced while maintaining this state. A water-containing yarn of 80% by weight or more is brought into contact with a silicon alkoxide solution to impregnate the fiber with the silicon alkoxide, and then dried at 200° C. or higher to contain 0.5 to 10% by weight of silica based on the dry fiber. This is a method for producing para-oriented aromatic polyamide fibers.

The "para-oriented aromatic polyamide" as used in the present invention refers to a polymer in which one or more divalent aromatic groups are directly bonded via amide groups, and the divalent bond of the aromatic groups is The groups are 1, 4-phenyl ethylene (paraphenylene), 4
．． 4'-bisphenylene and 1,4-naphthylene, which are arranged coaxially in the opposite direction from the aromatic ring, or 1,5-naphthylene and 2,6-naphthylene, which are arranged in the opposite direction along a parallel axis. Refers to aromatic polyamide. In addition to the above-mentioned monocyclic or polycyclic carbocyclic aromatic groups, examples of the aromatic group include 2,5-pyridazine, (wherein, X represents one leaf, -3-, or -NH-). It may also be a heterocyclic aromatic such as.

Typical examples of these para-oriented aromatic polyamides include polyparabenzamide, polyparaphenylene terephthalamide, poly-4,4'-diaminobenzanilide terephthalamide, poly-N.

N'-p-phenylenebis(p-benzamide) terephthalamide, polyparaphenylene-2,6-naphthalicamide, coparaphenylene/4,4'-(3,3'-dimethylbiphenylene)-terephthalamide, copolyparaphenylene/ 2,5-pyridylene-terephthalamide,
Examples include coparaphenylene terephthalamide/pyromellitimide, coparaphenylene-isocincomelonamide/terephthalamide, and the like.

In the para-oriented aromatic polyamide used in the present invention, up to 5 mol% of the aromatic groups constituting the molecule are divalent aromatic groups other than the above-mentioned special aromatic groups, such as metaphenylene groups, 3 .Replacement with 3'-biphenylene, etc. or divalent aliphatic groups such as ethylene, butylene, etc., and replacement of 5 mol% or less of amide bonds with ester bonds, urea bonds, urethane bonds, etc. are also allowed. .

The method for producing these para-oriented aromatic polyamides is not limited to the implementation of the present invention, and for example, the method for producing the para-oriented aromatic polyamide from the corresponding diamine and diacid chloride is disclosed in Japanese Patent Publication No. 35-14
It can be easily produced by a low-temperature solution polymerization method known from Publication No. 399 and the like.

The optically anisotropic dope used in the present invention is prepared by dissolving these para-oriented aromatic polyamides in a sulfuric acid solvent. The solvent preferably used is concentrated sulfuric acid of 95% by weight or more or fuming sulfuric acid, and other sulfuric acid-based solvents include chlorosulfuric acid, fluorosulfuric acid, and the like. The concentration of concentrated sulfuric acid is preferably 95% by weight or more, particularly when dissolving a polymer having a high intrinsic viscosity at a high concentration, 97% by weight or more.
．． The amount used is 5% by weight, more preferably 99% by weight or more.

The optically anisotropic dope used in the present invention is obtained at a polymer concentration higher than a certain level determined by the temperature of the polymer solvent and solution, and specifically, the optical anisotropy is observed for several combinations. should be confirmed. Optical anisotropy can be confirmed by placing a thinly stretched dope prepared on a slide glass between crossed nicols of a polarizing microscope, and the dark field of the crossed nicols changes to bright field. It can also be confirmed by the fact that when it is dissolved, it is oriented under shearing force and reflects light diffusely, producing a metallic or pearl-like luster. Generally speaking, the higher the polymer concentration of the spinning dope, the easier it is to obtain high-performance fibers, so it is desirable that the polymer concentration is high. Usually, it is used in an amount of at least 15% by weight or more. If the concentration is too low, high performance fibers with a density of at least 1.41 g/cfIr will not be obtained. However, if the concentration is too high, for example 22% by weight or more, the viscosity of the dope becomes too high, so it is necessary to set the dope temperature high, which tends to cause difficulties in the spinning operation. Therefore, the preferred polymer concentration of the spinning dope is 16-20% by weight.

When preparing and using the dope, in the above polymer concentration range, the dope may solidify near room temperature, so it may be handled at a temperature from room temperature to about 80°C.

However, from the viewpoint of avoiding decomposition of the polymer as much as possible, it is preferable to select a temperature as low as possible unless it solidifies.

It is recognized that the spinning dope prepared in this manner has optical anisotropy within the above polymer concentration and doping temperature ranges. Once such dope is passed through a spinneret,
It is forced into the air and then led into a coagulation bath.

Since the coagulating or coagulated yarn in the coagulation bath is hardly stretched, the discharged dope is drawn in the air directly below the nozzle and is stretched. In this stretching, if the stretching rate is low, the physical properties 9 of the fiber, such as strength and initial modulus, cannot be sufficiently increased, and the dope flow is cut off at too high a point, so the stretching rate is usually 4. -15 times, preferably between 5 and 12 times.

The length in air over which the dope is stretched, i.e.
The distance from the surface of the spinning nozzle where the dope is discharged to the surface of the coagulating solution is usually about 1 to 50 mm, preferably 3 to 20 mm.
Although it is set within the range of a circle, it is not limited to this. Specifically, the dope discharge rate from the spinning nozzle,
It is determined in consideration of the above-mentioned draft rate, reducing the chance of fusion of filaments, etc.

In the fiber manufacturing method of the present invention, it is important that the spinning nozzle and the coagulation bath are separated from each other in order to obtain fibers with excellent mechanical properties.

The pore diameter of the spinning nozzle used for discharging the dope is
It is selected depending on the thickness of the fiber to be manufactured and the draft rate setting above, and is usually 0.05 to 0.10 mm.
Although the range is selected, it is not limited to this range. Further, the number of holes provided in the spinning nozzle is determined by the structure of the fiber to be produced, and is not particularly limited when carrying out the present invention.

Water or an aqueous sulfuric acid solution having a concentration of up to 70% is usually advantageously used as the coagulation bath. However, for example, salts such as ammonium chloride, calcium chloride, calcium carbonate, sodium chloride, sodium sulfate, etc., or aqueous solutions of mixtures thereof, organic solvents such as methanol, ethanol, ethylene glycol, or aqueous solutions thereof, etc. may be used, and is not particularly limited.

Generally, the temperature of the coagulating liquid is preferably maintained at 15° C. or lower. This is because the lower the coagulation bath temperature, the smaller the amount of voids generated inside, the higher the density, and the better the mechanical performance such as strength. Note that the lower limit of the coagulation bath temperature is not particularly limited, and is up to the melting point (freezing point) determined by the composition of the coagulation bath.

The fibers pulled out from the coagulation bath are substantially neutralized and washed to remove the solvent and coagulation bath composition with water or aqueous alkali in a manner similar to conventional methods.

In the method for producing fibers of the present invention, it is necessary to release the tension acting on the fibers during coagulation and/or during the washing process in which a large amount of residual acid is present. This is important in order to increase the effect of silicon alkoxide impregnation, even though the fiber has a dense structure. The reason is,
Although the details have not yet been elucidated, it is presumed that there is a delicate relationship with the orientation of the molecular chains of the gel-like fibers swollen with water, the formation of crystals, etc.

It is difficult under industrial production methods and conditions to substantially release the tension from the threads during coagulation in the production of fibers. It is best to rinse with water without stress. As for such a method, it is industrially convenient to transfer the remaining solvent-containing yarn from the coagulation bath onto a net conveyor and wash it there under no tension. The time to release the tension from the coagulated filament is when the amount of residual solvent in the filament is at least 5% by weight, more preferably at least 10% by weight relative to the dry fiber. This is important for making alkoxide impregnation effective. On the other hand, if the tension is released only after the coagulation and washing have proceeded until the residual solvent is less than 5% by weight, the impregnation will not be sufficient.

The coagulated fiber threads are taken out of the spinning bath in the coagulated state via a suitable device such as a take-off roll, and are thrown onto a conveyor for processing by a transfer device.

It is important to avoid stretching the fiber threads as much as possible during the process until the fiber threads are drawn out from the coagulation bath and transferred onto the processing conveyor. The elongation treatment of unwashed coagulated filaments, which is often used to increase strength in the production of conventional recycled fibers and synthetic fibers, is probably due to the fact that the gel-like coagulated filament-like structure becomes more dense. This is not preferable because impregnation becomes difficult and requires a lot of time. However, in reality, it is unavoidable that tension is applied to the yarn due to the tension required to pull out the fibers from the coagulation bath and the frictional force in guides, transfer devices, etc. Tension is approximately 0.5
g/d or less, in particularly well-designed equipment approximately 0.2
g/d or less, which is lower than when elongation is actively applied, so it can be ignored in many cases.

The transfer device used for manufacturing the fiber of the present invention is as follows:
A single or pair of cage rolls, a single or a pair of gear-shaped rolls, etc. are rotated at a circumferential speed that is approximately equal to or higher than that of the yarn, and together with a flow of fluid such as water. Fluid flow ejectors, suction and delivery using air suckers, etc. are used.

Depending on the case, the threads shaken off by the transfer device may be directly deposited on a processing conveyor, but once
After forming a margin by shaking it off onto another endless conveyor or roller, it is preferable to place the margin on a processing conveyor with the upper and lower surfaces of the margin reversed. In contrast, when picking up the yarn from the margin after processing, the yarn is taken out from below the margin when there is no reversal operation, which causes inconveniences such as tangles and fuzzy yarn.
This is because such a problem does not occur when performing the above-described inversion processing.

In performing such a reversing operation, the reversing conveyor or roller moves or rotates at approximately the same linear speed as the processing conveyor, but depending on the thickness of the margin and the material and shape of the reversing conveyor or roller, the reversing conveyor or roller may move or rotate at a different speed as appropriate. It is preferable to set it to . The structure of the processing conveyor must be such that the washing water or other processing liquid flows or permeates through the belt, and usually, net-like, knitted fabric-like, string-like structures are preferably used. As a special example, it may be a structure in which perforated plates are connected together.

Furthermore, the material of the processing conveyor needs to be able to withstand the coagulating liquid that adheres to the yarns and the chemicals applied during the processing process, and it is more preferable that the material can withstand the heating during the drying process and the heat treatment process. It is desirable that there be little dimensional change during use.

For example, a stainless steel wire mesh or perforated plate, a glass fiber knitted fabric, a fluororesin-coated glass fiber net, a fluororesin fiber knitted fabric, a perforated plate or a perforated sheet of fluororesin are used.

The moving speed of the processing conveyor needs to be set slower than the yarn supply speed, that is, the take-up speed from the spinning bath, and the normal transfer rate (yarn speed/processing conveyor speed; the same applies hereinafter). It is set to about 1.2 times or more, particularly preferably about 10 times or more.

If it is lower than that, the yarn transferred on the processing conveyor will be at least partially elongated, causing partial tension in the yarn during the water washing and/or compression property improver impregnation treatment process. This method should be avoided because it is impossible to completely perform the process in a substantially stress-free state, which is the objective of the present invention.

The thread density in the processing conveyor system is adjusted by the transfer rate and transfer width, and is usually 0.005 on a dry system basis.
~0.2g/cnr, particularly preferably 0.005~0
．． The range is selected to be 1 g/cnr. Further, the transfer rate is selected to be <1.2 times or more as described above, with an upper limit of up to 1000 times, particularly preferably between 10 times and 2000 times. Specifically, the transfer width in the system can be determined by changing the falling distance from the transfer device to the reversing device or processing conveyor, or by changing the traversing device (traverser) before or after the transfer device.
This can be adjusted by installing a swing-type chute after the transfer device, and it varies depending on the total denier and rigidity of the fiber yarn, but in general, the special In some cases, it is also possible to set the distance to around 1 meter.

Moreover, the yarn transferred onto one processing conveyor is -
It is not limited to a book, but a large number of yarns are simultaneously transferred at appropriate intervals, and placed on a processing conveyor at appropriate intervals, for example, at intervals of several tens of millimeters from about IM, as a system of many strips. It is also an industrially preferred embodiment from the viewpoint of productivity to deposit, wash with water, and impregnate with silicon alkoxide at the same time.

The system, which is deposited on a processing conveyor, moves with the conveyor and is first led to a washing step to remove the solvent from the yarn, and then impregnated with silicon alkoxide in an impregnating step.

In the water washing process, preferably, the washing water is supplied onto the margin from a perforated plate in the form of a shower, from a spray nozzle in the form of a mist, or along a large number of brush-like fibers. The contained coagulating liquid is washed and passed through a processing conveyor and discharged below the conveyor. Here, the method of supplying the washing water is not limited in carrying out the present invention,
It is not limited to the above example.

For the purpose of complete coagulation or recovery of the coagulated liquid prior to the water washing process, the coagulated liquid or a mixture of the coagulated liquid and water, or a neutralizing agent or other processing liquid is used in the same manner as the water washing process. It may also be supplied into the system for treatment. Although it is desirable to completely remove the solvent and the like from the yarn by washing with water, in reality, if the concentration is 11,000 pp or less, the effect thereof can often be ignored.

In order to enhance the effect of water washing, it is also desirable to perform treatment with an arbitrary number of squeezing rolls or the like prior to water washing, and/or during or after the water washing process. For the same purpose, it is also preferable to increase the flow rate of the washing water flowing through the system and through the processing conveyor by suctioning it from below the processing conveyor. Elevating the water temperature may also be carried out, and there is no particular limitation in producing the fibers of the present invention. The water-washed thread pile must be kept in a water content of at least 80% by weight without being dried in a substantially stress-free state, and must be brought into contact with a solution containing silicon alkoxide. Water content is 80% by weight
If it is less than that, the fiber is in a so-called half-dried or dried state, and the rate of diffusion of the impregnating agent from the silicon alkoxide-impregnating solution into the interior of the fiber is significantly reduced, making it impossible to impregnate a substantial amount.

The silicon alkoxide used in the present invention may be a tetraalkoxysilane such as silicon tetraethoxide, silicon tetramethoxide, silicon tetraisopropoxide, silicon tetrabutoxide, or a composite alkoxide consisting of these alkoxides, and is not particularly limited.

The solvent for silicon alkoxide used for impregnation in producing the fibers of the present invention is not particularly limited as long as it is miscible with water, but alcohol-based solvents are preferred, and particularly preferred are solvents that are compatible with the silicon alkoxide used. It's the same alcohol.

Moreover, this solvent may contain water.

The amount of silica contained in the fibers of the present invention should be between 0.5 and 10% by weight, preferably 0.5 and 3.0% by weight, based on the untreated fiber.

This content is a value determined from the weight ratio before and after the treatment when silica is made into silica by heat treatment after being impregnated with silicon alkoxide. If the amount of impregnation is less than 0.5% by weight, the desired compressive properties cannot be obtained, and if it exceeds 10% by weight, impregnation is difficult, and the solution concentration and impregnation time must be increased (to be practical) inferior to

The method of impregnation is carried out by applying a solution containing silicon alkoxide to the thread pile on the processing conveyor by spraying, showering, etc., using the same means as for washing with water, or by immersing the whole conveyor in the processing liquid.

Impregnation conditions should be set according to the amount of silicon alkoxide required for impregnating the fiber, and should be determined based on the type of polymer used, the type of silicon alkoxide, the single fiber denier, the density in the system, and the structure of the processing conveyor. etc., and it is desirable to determine it experimentally under each condition.

The temperature of the treatment liquid can be set arbitrarily between room temperature and the boiling point of the solvent used, but a high temperature is preferred in order to increase the rate of diffusion into the fibers.

The concentration of silicon alkoxide in the processing solution is usually 0, 1~
It is 60% by weight. The concentration of silicon alkoxide is 6
If it exceeds 0% by weight, the hydrophobicity of the solution becomes too high,
This is not preferred because it becomes difficult to impregnate the yarn containing water with silicon alkoxide.

On the other hand, the single fiber denier of the undried fibers used for impregnation is also an important factor. Generally, as the denier increases, the density decreases, but there is a difference in the diffusion rate that cannot be predicted from the slight difference in the density of the fibers after drying, and the amount of impregnation increases. Therefore, the preferred single yarn denier is 0 in the dry state.
．． It is 5 denier or more, particularly preferably 1.5 denier or more. This means that a slight difference in the density of the undried threads greatly affects the diffusion rate of silicon alkoxide. In particular, in the method for producing such fibers having a tensile strength of 20 g/d or more, i.e., the fiber density is preferably 1, 43 g/cff1 or more, tension is applied at the initial stage of fiber production. Impregnation with a releasing step is effective for producing the fibers of the present invention.

In drying such fibers, the drying temperature is 200°C or higher, preferably 200 to 250°C. This is because the structure of the fiber becomes denser by drying at high temperature, and once impregnated with silicon alkoxide, it becomes amorphous silica in the loose parts inside the fiber, reinforcing the weak parts of the fiber and improving the compressive properties of the fiber. This is because it becomes necessary to do so. As for the drying temperature, if necessary, heat treatment can be performed at a higher temperature to further increase the compression properties, but at the same time deterioration of the fiber will occur, so a range of 200 to 250°C is suitable for maintaining the performance of the fiber. be. Furthermore, high modulus can be achieved by stretching after impregnation, prior to drying, or simultaneously with drying. Further, high elongation can be obtained by drying under low tension or no tension. Furthermore, in the method for producing fibers of the present invention, since the fibers are impregnated with silicon alkoxide in an undried state and then heat treated to contain silica, there is almost no deterioration in physical properties.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.
These examples are not intended to limit the invention in any way.

In the examples, "%" and "parts" represent weight percent and parts by weight, respectively, unless otherwise specified. Further, the main various parameters used in the present invention were measured as follows.

Measuring method of strength, elongation and elongation of fibers The strength, elongation and initial modulus of fiber yarns can be measured by
According to the IS standard, the yarn, which had been twisted 8 times per 10 cm prior to measurement, was subjected to a load test using a fixed length elongation type strength and elongation tester at a gripping length of 20 cm and a tensile speed of 50%/min.
The elongation rate curve is drawn and read or calculated, and is expressed as the average value of 20 measurements.

Quantification of the amount of silica in the fibers The amount of silica in the fibers was determined by carbonizing 200 g of fibers at 500° C. and then burning them at 800° C. for 3 hours to completely incinerate them. After adding 5 g of sodium carbonate to this and melting it, it was solidified, and 10% by weight hydrochloric acid was added and dissolved. After this solution was quantified as Si by plasma emission spectrometry, the value was expressed as silica in weight percent relative to the dry fiber.

Reference Example 1 Method for producing poly-para-phenylene terephthalamide Poly-para-phenylene terephthalamide (hereinafter abbreviated as PPTA) was obtained as follows by a low temperature solution polymerization method.

In the polymerization apparatus shown in Japanese Patent Publication No. 53-43968, 7 parts of anhydrous lithium chloride was added to 1000 parts of N-methylpyrrolidone.
Dissolve 0 parts, then paraphenylenediamine 48.6
part was dissolved. After cooling to 8° C., 91.4 parts of terephthalic acid dichloride was added at once in powder form. After a few minutes, the polymerization reaction product solidified into a cheese-like shape, so it was
According to the method described in 43986, the polymerization reaction product was discharged from the polymerization apparatus and immediately transferred to a twin-screw sealed kneader.
The polymerization reaction product was pulverized in the same kneader. Next, the finely ground product was transferred to a Henschel mixer, an approximately equal amount of water was added thereto, and after further grinding, it was filtered, washed several times in hot water, and dried in hot air at 110°C. Light yellow PPT with ηinh of 5.0
A: 95 copies were obtained.

Note that polymers with different ηinh can be easily obtained by changing the ratio of N-methylpyrrolidone and monomers (para-phenylenediamine and terephthalic acid chloride), and/or the ratio between monomers.

Examples 1 to 5 PPTA with an intrinsic viscosity (η1nh) of 7.05 was added to 99.7% concentrated sulfuric acid so that the polymer concentration was 18.7%.
The polymer solution was melted while maintaining the temperature at 80° C. to prepare a polymer solution for spinning (hereinafter abbreviated as dope). This polymer solution was observed to exhibit optical anisotropy using a polarizing microscope under crossed Nicols.

This dope was left to stand under vacuum for 2 hours to defoam, and then used for spinning.

The dope was passed through a gear pump and filtered using a candle filter made of eight layers of 300 mesh stainless steel wire mesh, and then extruded into a coagulation bath through a spinning nozzle with a pore diameter of 0.07 mm and 100 holes through 5 mm of air. did. At that time, the coagulating liquid was 1
A 0% aqueous sulfuric acid solution was used. Next, the yarn introduced into the coagulation liquid was changed direction by a direction change roll and led to a Nelson roll. At this time, the amount of residual sulfuric acid in the fiber was 17.3 as a dry fiber weight ratio.
%Met. The yarn pulled by the Nelson roll is
Next, the yarn is transferred onto a reversing net using a device disclosed in Japanese Patent Publication No. 55-9088, that is, a pair of gear nip rolls (rolls in which gear-shaped rolls are shallowly engaged and the yarn is sent out between them), and then processed. It was placed upside down on a net conveyor. After the blank space placed on the processing conveyor is washed with water using a one-way shower, an ethanol solution of silicone tetraethoxide is added to it in the impregnating process with a water content of about 420%, as shown in Table 1, using the same one-way shower. After showering at the concentration, temperature, and impregnation time shown in , and drying at 250° C., the yarn was wound with a winder.

For comparison, an example in which water was showered in the impregnation step is also shown in Table 1 as Comparative Example 1.

Comparative Example 2 After spinning in the same manner as in Examples 1 to 5, the once dried yarn was impregnated in the same manner as in Example 3. Table 1 shows the results.

Comparative Example 3 After spinning in the same manner as in Examples 1 to 5, the same operation as in Example 3 was performed in a water-containing state of about 50%. The results are shown in Table 1.

Reference example 2 Evaluation method of compression properties as a unidirectional laminate Epoxy resin (
Manufactured by Kasei Fiberlite Co., Ltd., #7714) has a solid content of 50
While impregnating the para-oriented aromatic polyamide fibers obtained in Examples 1 to 5 and Comparative Examples 1 to 3, which were aligned in one direction, in a methyl ethyl ketone solution adjusted to be % by weight,
This was wound up on a 500Mφ drum wrapped with silicone release paper. Cut this in the direction perpendicular to the fiber direction 1
A unidirectional prepreg was prepared by heating at 00°C for 30 minutes.

The volume content of the fiber at this time is 63%, and the thickness is approximately 0.2
It was mm. The obtained prepreg is 150mm x 1
Cut into 50 mm pieces, stack the pieces to a specified thickness, and place in an autoclave at 140°C for 3 hours.
A flat plate was obtained by hardening and molding under nitrogen pressure of 4 kg/car. Width 12.8m+ with 2mm tabs on both sides as a sample for measuring compressive strength.

A compression test piece having a length of 80.8 mm was cut out, and the compressive fracture strength was measured using a universal testing machine (AG-IOTA) manufactured by Shimadzu Corporation at a crosshead speed of 1.3 mm/min using 5 test pieces. The results are summarized in Table 1.

(The following is a blank space) Examples 6 to 7 All operations were carried out in the same manner as in Example 1 except that silicon tetraethoxide was replaced with the compound shown in Table 2. The results are shown in Table 2.

(The following is a blank space) [Effects] All of the fibers obtained by the present invention can be compressed without causing a decrease in original tensile strength and initial modulus, compared to fibers obtained by conventionally known methods. It was recognized that the properties were excellent.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] An optically anisotropic dope in which a para-oriented aromatic polyamide is dissolved in concentrated sulfuric acid with a concentration of 95 to 101% by weight to give a polymer concentration of at least 15% by weight is passed through an orifice into air and then into a coagulation bath. After pushing out to
In a method for producing para-oriented aromatic polyamide fibers in which yarns are drawn out from a coagulation bath, washed with water, and dried, tension is substantially released from the coagulated yarns during coagulation or in the initial stage of washing containing 5% or more of sulfuric acid per dry fiber. Then, while maintaining this state, a water-containing yarn having a water content of 80% by weight or more is brought into contact with a silicon alkoxide solution to impregnate the silicon alkoxide, and then dried at 200°C or higher to form silica at a concentration of 0.0% relative to the dry fiber. A method for producing para-oriented aromatic polyamide fiber, characterized by containing 5 to 10% by weight